{"kind": "conn", "major": "18", "item": {"slug": "min-protocol-version", "name": "min_protocol_version", "name_zh": "", "category": "Session and protocol", "summary": "Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed.", "aliases": ["PGMINPROTOCOLVERSION", "min_protocol_version"], "content_hash": "823873a9dcc4160c141586cd34d25496936fd3bf4d2807419fe6427cd8740887", "versions": {"18": {"facts": [{"label": "Client library", "value": "libpq 18.6"}, {"label": "Manual definition", "value": "Documented"}, {"label": "Source environment fallback", "value": "PGMINPROTOCOLVERSION"}, {"label": "Compiled fallback expression", "value": "NULL"}], "tables": [{"key": "environment", "rows": [{"name": {"url": "/docs/18/libpq-envars.html", "text": "PGMINPROTOCOLVERSION"}, "description": "PGMINPROTOCOLVERSION behaves the same as the min_protocol_version connection parameter."}], "title": "Environment fallback", "columns": [{"key": "name", "label": "Variable"}, {"key": "description", "label": "Documented behavior"}]}], "keyword": "min_protocol_version", "related": [{"url": "/docs/18/libpq-pgservice.html", "label": "Connection service file"}, {"url": "/docs/18/libpq-pgpass.html", "label": "Password file"}, {"url": "/docs/18/libpq-envars.html", "label": "All libpq environment variables"}], "release": {"ref": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "label": "18.6", "major": "18", "channel": "stable", "manifest": {"pdf": {"A4": {"url": "/files/documentation/pdf/18/postgresql-18-A4.pdf", "bytes": 15865106, "pages": 3154, "sha256": "19512c405da53f9f7fcf0abba359223aa65f021be025bf3411381918f92e3190", "built_at": "2026-09-26"}, "US": {"url": "/files/documentation/pdf/18/postgresql-18-US.pdf", "bytes": 15748059, "pages": 3328, "sha256": "facbe6c229e598b872d3d98bef53308f46e06746006fa4590de9a7de9dd46319", "built_at": "2026-09-26"}}, "tree": "18", "index": "index.html", "major": "18", "pages": 1148, "release": "18.6", "source_url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "svg_assets": 3, "source_mode": "en SGML built with pinned official archive", "source_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "revision": "ee8d1a3612338fd9adf250730cb640fcc5233b5491337cc00a316a44e3a0b9f8", "evidence_kind": "English manual and source declarations", "source_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "sources": [{"url": "/docs/18/libpq-connect.html#LIBPQ-CONNECT-MIN-PROTOCOL-VERSION", "file": "libpq-connect.html", "label": "18.6 English manual \u00b7 libpq-connect.html", "anchor": "LIBPQ-CONNECT-MIN-PROTOCOL-VERSION", "sha256": "c26a7fc3dcda6066cfe540641ae2690faf3d3c03277f30b4dfc2328ab45c212f"}, {"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "file": "src/interfaces/libpq/fe-connect.c", "label": "18.6 libpq connection option declarations", "sha256": "44a6e386cbfd67ebe768d6ef5493098119c2e6b4796239d53e5ed7b122b206a5", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "/docs/18/libpq-envars.html", "file": "libpq-envars.html", "label": "18.6 English manual \u00b7 libpq-envars.html", "anchor": "", "sha256": "d64db73f3d48127bb984a5f775e77b7bcca2ba4bd218333cf24a45fcdd7c4363"}, {"url": "/docs/18/libpq-pgservice.html", "file": "libpq-pgservice.html", "label": "18.6 English manual \u00b7 libpq-pgservice.html", "anchor": "", "sha256": "6035a3f0ee1d0fd80db5bf58834390b884eecd23206659bdf6f07560deea5aa7"}], "sections": [{"title": "Default resolution and service-file precedence", "paragraphs": ["The following environment variables can be used to select default connection parameter values, which will be used by PQconnectdb , PQsetdbLogin and PQsetdb if no value is directly specified by the calling code. These are useful to avoid hard-coding database connection information into simple client applications, for example.", "Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . On Microsoft Windows, it is named %APPDATA%\\postgresql\\.pg_service.conf (where %APPDATA% refers to the Application Data subdirectory in the user's profile). A different file name can be specified by setting the environment variable PGSERVICEFILE . The system-wide file is named pg_service.conf . By default it is sought in the etc directory of the PostgreSQL installation (use pg_config --sysconfdir to identify this directory precisely). Another directory, but not a different file name, can be specified by setting the environment variable PGSYSCONFDIR .", "Connection parameters obtained from a service file are combined with parameters obtained from other sources. A service file setting overrides the corresponding environment variable, and in turn can be overridden by a value given directly in the connection string. For example, using the above service file, a connection string service=mydb port=5434 will use host somehost , port 5434 , user admin , and other parameters as set by environment variables or built-in defaults."]}, {"title": "Environment variable evidence", "paragraphs": ["PGMINPROTOCOLVERSION behaves the same as the min_protocol_version connection parameter."]}], "signature": "min_protocol_version", "documented": true, "description": ["Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed."], "environment": [{"name": "PGMINPROTOCOLVERSION", "source_url": "/docs/18/libpq-envars.html", "description": "PGMINPROTOCOLVERSION behaves the same as the min_protocol_version connection parameter."}], "manual_html": "<div><dl class=\"variablelist\"><dt id=\"LIBPQ-CONNECT-MIN-PROTOCOL-VERSION\"><span class=\"term\"><code class=\"literal\">min_protocol_version</code></span> </dt><dd>\n<p>Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the <span class=\"productname\">PostgreSQL</span> protocol supported by libpq, which currently means <code class=\"literal\">3.0</code>. If the server does not support at least this protocol version the connection will be closed.</p>\n<p>The current supported values are <code class=\"literal\">3.0</code>, <code class=\"literal\">3.2</code>, and <code class=\"literal\">latest</code>. The <code class=\"literal\">latest</code> value is equivalent to the latest protocol version supported by the libpq version being used, which is currently <code class=\"literal\">3.2</code>.</p>\n</dd></dl></div>", "manual_path": "libpq-connect.html#LIBPQ-CONNECT-MIN-PROTOCOL-VERSION", "source_option": {"keyword": "min_protocol_version", "declaration": "\"min_protocol_version\", \"PGMINPROTOCOLVERSION\", NULL, NULL, \"Min-Protocol-Version\", \"\", 6, offsetof(struct pg_conn, min_protocol_version)", "environment": "PGMINPROTOCOLVERSION", "source_notes": [], "compiled_default_expression": "NULL"}, "comparison_data": {"keyword": "min_protocol_version", "definition": "Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed. The current supported values are 3.0 , 3.2 , and latest . The latest value is equivalent to the latest protocol version supported by the libpq version being used, which is currently 3.2 .", "documented": true, "environment": "PGMINPROTOCOLVERSION", "default_evidence": ["Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed."], "compiled_default_expression": "NULL"}, "comparison_hash": "935c998892c3632ad1e984dcf59a08b726671ddc4efa152ef1d02f7922b2cba6", "default_evidence": ["Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed."], "precedence_evidence": ["The following environment variables can be used to select default connection parameter values, which will be used by PQconnectdb , PQsetdbLogin and PQsetdb if no value is directly specified by the calling code. These are useful to avoid hard-coding database connection information into simple client applications, for example.", "Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . On Microsoft Windows, it is named %APPDATA%\\postgresql\\.pg_service.conf (where %APPDATA% refers to the Application Data subdirectory in the user's profile). A different file name can be specified by setting the environment variable PGSERVICEFILE . The system-wide file is named pg_service.conf . By default it is sought in the etc directory of the PostgreSQL installation (use pg_config --sysconfdir to identify this directory precisely). Another directory, but not a different file name, can be specified by setting the environment variable PGSYSCONFDIR .", "Connection parameters obtained from a service file are combined with parameters obtained from other sources. A service file setting overrides the corresponding environment variable, and in turn can be overridden by a value given directly in the connection string. For example, using the above service file, a connection string service=mydb port=5434 will use host somehost , port 5434 , user admin , and other parameters as set by environment variables or built-in defaults."]}, "19": {"facts": [{"label": "Client library", "value": "libpq 19beta4"}, {"label": "Manual definition", "value": "Documented"}, {"label": "Source environment fallback", "value": "PGMINPROTOCOLVERSION"}, {"label": "Compiled fallback expression", "value": "NULL"}], "tables": [{"key": "environment", "rows": [{"name": {"url": "/docs/19/libpq-envars.html", "text": "PGMINPROTOCOLVERSION"}, "description": "PGMINPROTOCOLVERSION behaves the same as the min_protocol_version connection parameter."}], "title": "Environment fallback", "columns": [{"key": "name", "label": "Variable"}, {"key": "description", "label": "Documented behavior"}]}], "keyword": "min_protocol_version", "related": [{"url": "/docs/19/libpq-pgservice.html", "label": "Connection service file"}, {"url": "/docs/19/libpq-pgpass.html", "label": "Password file"}, {"url": "/docs/19/libpq-envars.html", "label": "All libpq environment variables"}], "release": {"ref": "https://ftp.postgresql.org/pub/source/v19beta4/postgresql-19beta4.tar.bz2", "label": "19beta4", "major": "19", "channel": "preview", "manifest": {"pdf": {"A4": {"url": "/files/documentation/pdf/19/postgresql-19-A4.pdf", "bytes": 16064841, "pages": 3052, "sha256": "4dd099e4125c591128fc5f3ebd02178dc24781f9e5ae629f96d67c4c8547427b", "built_at": "2026-09-26"}, "US": {"url": "/files/documentation/pdf/19/postgresql-19-US.pdf", "bytes": 15974616, "pages": 3225, "sha256": "61971fa857f0956d47341a0388fa6af9ae10acf691d4b2fc009007d384b0342b", "built_at": "2026-09-26"}}, "tree": "19", "index": "index.html", "major": "19", "pages": 1155, "release": "19beta4", "source_url": "https://ftp.postgresql.org/pub/source/v19beta4/postgresql-19beta4.tar.bz2", "svg_assets": 5, "source_mode": "en SGML built with pinned official archive", "source_sha256": "83157ee9c599d03b2f7a3d73ef3a56ec24e0e79cc2b3501a64d1364f56398c86"}, "revision": "1bbbbf4133d426f0e4304010688d2984c30fb67df0cc3a61b3e37eb3f6f37833", "evidence_kind": "English manual and source declarations", "source_sha256": "83157ee9c599d03b2f7a3d73ef3a56ec24e0e79cc2b3501a64d1364f56398c86"}, "sources": [{"url": "/docs/19/libpq-connect.html#LIBPQ-CONNECT-MIN-PROTOCOL-VERSION", "file": "libpq-connect.html", "label": "19beta4 English manual \u00b7 libpq-connect.html", "anchor": "LIBPQ-CONNECT-MIN-PROTOCOL-VERSION", "sha256": "14917417235a95d969bf3642c347dea7ae548c5f73b0dd00991a580ebcfbb47e"}, {"url": "https://ftp.postgresql.org/pub/source/v19beta4/postgresql-19beta4.tar.bz2", "file": "src/interfaces/libpq/fe-connect.c", "label": "19beta4 libpq connection option declarations", "sha256": "ae8005372c570ff47a4922c942238653a034f01f9db40c9e0f57cb48915ffd98", "archive_sha256": "83157ee9c599d03b2f7a3d73ef3a56ec24e0e79cc2b3501a64d1364f56398c86"}, {"url": "/docs/19/libpq-envars.html", "file": "libpq-envars.html", "label": "19beta4 English manual \u00b7 libpq-envars.html", "anchor": "", "sha256": "d8f0afee19bae6323942ea5415649fbd66e3880fe8c8415350fcf3915f7c7047"}, {"url": "/docs/19/libpq-pgservice.html", "file": "libpq-pgservice.html", "label": "19beta4 English manual \u00b7 libpq-pgservice.html", "anchor": "", "sha256": "4c858fe55701d703cc00e7adf55eeac09cafcfdc37929b8e23ccf8ba42af9f98"}], "sections": [{"title": "Default resolution and service-file precedence", "paragraphs": ["The following environment variables can be used to select default connection parameter values, which will be used by PQconnectdb , PQsetdbLogin and PQsetdb if no value is directly specified by the calling code. These are useful to avoid hard-coding database connection information into simple client applications, for example.", "Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . On Microsoft Windows, it is named %APPDATA%\\postgresql\\.pg_service.conf (where %APPDATA% refers to the Application Data subdirectory in the user's profile). A different file name can be specified using the servicefile key word in a libpq connection string or by setting the environment variable PGSERVICEFILE . The system-wide file is named pg_service.conf . By default it is sought in the etc directory of the PostgreSQL installation (use pg_config --sysconfdir to identify this directory precisely). Another directory, but not a different file name, can be specified by setting the environment variable PGSYSCONFDIR .", "Connection parameters obtained from a service file are combined with parameters obtained from other sources. A service file setting overrides the corresponding environment variable, and in turn can be overridden by a value given directly in the connection string. For example, using the above service file, a connection string service=mydb port=5434 will use host somehost , port 5434 , user admin , and other parameters as set by environment variables or built-in defaults."]}, {"title": "Environment variable evidence", "paragraphs": ["PGMINPROTOCOLVERSION behaves the same as the min_protocol_version connection parameter."]}], "signature": "min_protocol_version", "documented": true, "description": ["Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed."], "environment": [{"name": "PGMINPROTOCOLVERSION", "source_url": "/docs/19/libpq-envars.html", "description": "PGMINPROTOCOLVERSION behaves the same as the min_protocol_version connection parameter."}], "manual_html": "<div><dl class=\"variablelist\"><dt id=\"LIBPQ-CONNECT-MIN-PROTOCOL-VERSION\"><span class=\"term\"><code class=\"literal\">min_protocol_version</code></span> </dt><dd>\n<p>Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the <span class=\"productname\">PostgreSQL</span> protocol supported by libpq, which currently means <code class=\"literal\">3.0</code>. If the server does not support at least this protocol version the connection will be closed.</p>\n<p>The current supported values are <code class=\"literal\">3.0</code>, <code class=\"literal\">3.2</code>, and <code class=\"literal\">latest</code>. The <code class=\"literal\">latest</code> value is equivalent to the latest protocol version supported by the libpq version being used, which is currently <code class=\"literal\">3.2</code>.</p>\n</dd></dl></div>", "manual_path": "libpq-connect.html#LIBPQ-CONNECT-MIN-PROTOCOL-VERSION", "source_option": {"keyword": "min_protocol_version", "declaration": "\"min_protocol_version\", \"PGMINPROTOCOLVERSION\", NULL, NULL, \"Min-Protocol-Version\", \"\", 6, offsetof(struct pg_conn, min_protocol_version)", "environment": "PGMINPROTOCOLVERSION", "source_notes": [], "compiled_default_expression": "NULL"}, "comparison_data": {"keyword": "min_protocol_version", "definition": "Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed. The current supported values are 3.0 , 3.2 , and latest . The latest value is equivalent to the latest protocol version supported by the libpq version being used, which is currently 3.2 .", "documented": true, "environment": "PGMINPROTOCOLVERSION", "default_evidence": ["Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed."], "compiled_default_expression": "NULL"}, "comparison_hash": "935c998892c3632ad1e984dcf59a08b726671ddc4efa152ef1d02f7922b2cba6", "default_evidence": ["Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed."], "precedence_evidence": ["The following environment variables can be used to select default connection parameter values, which will be used by PQconnectdb , PQsetdbLogin and PQsetdb if no value is directly specified by the calling code. These are useful to avoid hard-coding database connection information into simple client applications, for example.", "Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . On Microsoft Windows, it is named %APPDATA%\\postgresql\\.pg_service.conf (where %APPDATA% refers to the Application Data subdirectory in the user's profile). A different file name can be specified using the servicefile key word in a libpq connection string or by setting the environment variable PGSERVICEFILE . The system-wide file is named pg_service.conf . By default it is sought in the etc directory of the PostgreSQL installation (use pg_config --sysconfdir to identify this directory precisely). Another directory, but not a different file name, can be specified by setting the environment variable PGSYSCONFDIR .", "Connection parameters obtained from a service file are combined with parameters obtained from other sources. A service file setting overrides the corresponding environment variable, and in turn can be overridden by a value given directly in the connection string. For example, using the above service file, a connection string service=mydb port=5434 will use host somehost , port 5434 , user admin , and other parameters as set by environment variables or built-in defaults."]}, "20": {"facts": [{"label": "Client library", "value": "libpq 20devel"}, {"label": "Manual definition", "value": "Documented"}, {"label": "Source environment fallback", "value": "PGMINPROTOCOLVERSION"}, {"label": "Compiled fallback expression", "value": "NULL"}], "tables": [{"key": "environment", "rows": [{"name": {"url": "/docs/devel/libpq-envars.html", "text": "PGMINPROTOCOLVERSION"}, "description": "PGMINPROTOCOLVERSION behaves the same as the min_protocol_version connection parameter."}], "title": "Environment fallback", "columns": [{"key": "name", "label": "Variable"}, {"key": "description", "label": "Documented behavior"}]}], "keyword": "min_protocol_version", "related": [{"url": "/docs/devel/libpq-pgservice.html", "label": "Connection service file"}, {"url": "/docs/devel/libpq-pgpass.html", "label": "Password file"}, {"url": "/docs/devel/libpq-envars.html", "label": "All libpq environment variables"}], "release": {"ref": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "label": "20devel", "major": "20", "channel": "devel", "manifest": {"pdf": {"A4": {"url": "/files/documentation/pdf/20/postgresql-20-A4.pdf", "bytes": 16030631, "pages": 3052, "sha256": "bd5d82c0ce38fc18f92a0447818a91a193a261776bca1c37564bf9a683e177d0", "built_at": "2026-09-28"}, "US": {"url": "/files/documentation/pdf/20/postgresql-20-US.pdf", "bytes": 15936613, "pages": 3223, "sha256": "d97d9e0db479a02f4234b175f50fcad70c3661619afc8d6df9b9437882e3c299", "built_at": "2026-09-28"}}, "tree": "0", "index": "index.html", "major": "20", "pages": 1156, "release": "20devel", "source_url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "svg_assets": 6, "source_mode": "en SGML built with pinned official archive", "source_sha256": "4d3346909b201ac1648232cf290462a7070c119326f56196f1f0253ed80fae41", "source_snapshot_utc": "26-Sep-2026 20:22"}, "revision": "2eba5e0fd4c3bffb2803247b6cd537878e9d6ee5a6dfbe3c50ece8b421b80918", "evidence_kind": "English manual and source declarations", "source_sha256": "4d3346909b201ac1648232cf290462a7070c119326f56196f1f0253ed80fae41"}, "sources": [{"url": "/docs/devel/libpq-connect.html#LIBPQ-CONNECT-MIN-PROTOCOL-VERSION", "file": "libpq-connect.html", "label": "20devel English manual \u00b7 libpq-connect.html", "anchor": "LIBPQ-CONNECT-MIN-PROTOCOL-VERSION", "sha256": "eeb28ce798c0f99c3581400b4baaae7687ee5d4176fcb9f5d2fd28809282d48f"}, {"url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "file": "src/interfaces/libpq/fe-connect.c", "label": "20devel libpq connection option declarations", "sha256": "d6eab6e2f37054b32a7ee7039b53beae603316f8ec3f0a14716061e042fc4aa1", "archive_sha256": "4d3346909b201ac1648232cf290462a7070c119326f56196f1f0253ed80fae41"}, {"url": "/docs/devel/libpq-envars.html", "file": "libpq-envars.html", "label": "20devel English manual \u00b7 libpq-envars.html", "anchor": "", "sha256": "7c49cf204e26ea86654491db5ea06c4f558c670e2e60a60b1dbf708ce682accc"}, {"url": "/docs/devel/libpq-pgservice.html", "file": "libpq-pgservice.html", "label": "20devel English manual \u00b7 libpq-pgservice.html", "anchor": "", "sha256": "a1ccd63a6e307a5541d58eabd57be5b467dff2480770838ec9b6a59a3ef110dc"}], "sections": [{"title": "Default resolution and service-file precedence", "paragraphs": ["The following environment variables can be used to select default connection parameter values, which will be used by PQconnectdb , PQsetdbLogin and PQsetdb if no value is directly specified by the calling code. These are useful to avoid hard-coding database connection information into simple client applications, for example.", "Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . On Microsoft Windows, it is named %APPDATA%\\postgresql\\.pg_service.conf (where %APPDATA% refers to the Application Data subdirectory in the user's profile). A different file name can be specified using the servicefile key word in a libpq connection string or by setting the environment variable PGSERVICEFILE . The system-wide file is named pg_service.conf . By default it is sought in the etc directory of the PostgreSQL installation (use pg_config --sysconfdir to identify this directory precisely). Another directory, but not a different file name, can be specified by setting the environment variable PGSYSCONFDIR .", "Connection parameters obtained from a service file are combined with parameters obtained from other sources. A service file setting overrides the corresponding environment variable, and in turn can be overridden by a value given directly in the connection string. For example, using the above service file, a connection string service=mydb port=5434 will use host somehost , port 5434 , user admin , and other parameters as set by environment variables or built-in defaults."]}, {"title": "Environment variable evidence", "paragraphs": ["PGMINPROTOCOLVERSION behaves the same as the min_protocol_version connection parameter."]}], "signature": "min_protocol_version", "documented": true, "description": ["Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed."], "environment": [{"name": "PGMINPROTOCOLVERSION", "source_url": "/docs/devel/libpq-envars.html", "description": "PGMINPROTOCOLVERSION behaves the same as the min_protocol_version connection parameter."}], "manual_html": "<div><dl class=\"variablelist\"><dt id=\"LIBPQ-CONNECT-MIN-PROTOCOL-VERSION\"><span class=\"term\"><code class=\"literal\">min_protocol_version</code></span> </dt><dd>\n<p>Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the <span class=\"productname\">PostgreSQL</span> protocol supported by libpq, which currently means <code class=\"literal\">3.0</code>. If the server does not support at least this protocol version the connection will be closed.</p>\n<p>The current supported values are <code class=\"literal\">3.0</code>, <code class=\"literal\">3.2</code>, and <code class=\"literal\">latest</code>. The <code class=\"literal\">latest</code> value is equivalent to the latest protocol version supported by the libpq version being used, which is currently <code class=\"literal\">3.2</code>.</p>\n</dd></dl></div>", "manual_path": "libpq-connect.html#LIBPQ-CONNECT-MIN-PROTOCOL-VERSION", "source_option": {"keyword": "min_protocol_version", "declaration": "\"min_protocol_version\", \"PGMINPROTOCOLVERSION\", NULL, NULL, \"Min-Protocol-Version\", \"\", 6, offsetof(struct pg_conn, min_protocol_version)", "environment": "PGMINPROTOCOLVERSION", "source_notes": [], "compiled_default_expression": "NULL"}, "comparison_data": {"keyword": "min_protocol_version", "definition": "Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed. The current supported values are 3.0 , 3.2 , and latest . The latest value is equivalent to the latest protocol version supported by the libpq version being used, which is currently 3.2 .", "documented": true, "environment": "PGMINPROTOCOLVERSION", "default_evidence": ["Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed."], "compiled_default_expression": "NULL"}, "comparison_hash": "935c998892c3632ad1e984dcf59a08b726671ddc4efa152ef1d02f7922b2cba6", "default_evidence": ["Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed."], "precedence_evidence": ["The following environment variables can be used to select default connection parameter values, which will be used by PQconnectdb , PQsetdbLogin and PQsetdb if no value is directly specified by the calling code. These are useful to avoid hard-coding database connection information into simple client applications, for example.", "Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . On Microsoft Windows, it is named %APPDATA%\\postgresql\\.pg_service.conf (where %APPDATA% refers to the Application Data subdirectory in the user's profile). A different file name can be specified using the servicefile key word in a libpq connection string or by setting the environment variable PGSERVICEFILE . The system-wide file is named pg_service.conf . By default it is sought in the etc directory of the PostgreSQL installation (use pg_config --sysconfdir to identify this directory precisely). Another directory, but not a different file name, can be specified by setting the environment variable PGSYSCONFDIR .", "Connection parameters obtained from a service file are combined with parameters obtained from other sources. A service file setting overrides the corresponding environment variable, and in turn can be overridden by a value given directly in the connection string. For example, using the above service file, a connection string service=mydb port=5434 will use host somehost , port 5434 , user admin , and other parameters as set by environment variables or built-in defaults."]}}}, "snapshot": {"facts": [{"label": "Client library", "value": "libpq 18.6"}, {"label": "Manual definition", "value": "Documented"}, {"label": "Source environment fallback", "value": "PGMINPROTOCOLVERSION"}, {"label": "Compiled fallback expression", "value": "NULL"}], "tables": [{"key": "environment", "rows": [{"name": {"url": "/docs/18/libpq-envars.html", "text": "PGMINPROTOCOLVERSION"}, "description": "PGMINPROTOCOLVERSION behaves the same as the min_protocol_version connection parameter."}], "title": "Environment fallback", "columns": [{"key": "name", "label": "Variable"}, {"key": "description", "label": "Documented behavior"}]}], "keyword": "min_protocol_version", "related": [{"url": "/docs/18/libpq-pgservice.html", "label": "Connection service file"}, {"url": "/docs/18/libpq-pgpass.html", "label": "Password file"}, {"url": "/docs/18/libpq-envars.html", "label": "All libpq environment variables"}], "release": {"ref": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "label": "18.6", "major": "18", "channel": "stable", "manifest": {"pdf": {"A4": {"url": "/files/documentation/pdf/18/postgresql-18-A4.pdf", "bytes": 15865106, "pages": 3154, "sha256": "19512c405da53f9f7fcf0abba359223aa65f021be025bf3411381918f92e3190", "built_at": "2026-09-26"}, "US": {"url": "/files/documentation/pdf/18/postgresql-18-US.pdf", "bytes": 15748059, "pages": 3328, "sha256": "facbe6c229e598b872d3d98bef53308f46e06746006fa4590de9a7de9dd46319", "built_at": "2026-09-26"}}, "tree": "18", "index": "index.html", "major": "18", "pages": 1148, "release": "18.6", "source_url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "svg_assets": 3, "source_mode": "en SGML built with pinned official archive", "source_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "revision": "ee8d1a3612338fd9adf250730cb640fcc5233b5491337cc00a316a44e3a0b9f8", "evidence_kind": "English manual and source declarations", "source_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "sources": [{"url": "/docs/18/libpq-connect.html#LIBPQ-CONNECT-MIN-PROTOCOL-VERSION", "file": "libpq-connect.html", "label": "18.6 English manual \u00b7 libpq-connect.html", "anchor": "LIBPQ-CONNECT-MIN-PROTOCOL-VERSION", "sha256": "c26a7fc3dcda6066cfe540641ae2690faf3d3c03277f30b4dfc2328ab45c212f"}, {"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "file": "src/interfaces/libpq/fe-connect.c", "label": "18.6 libpq connection option declarations", "sha256": "44a6e386cbfd67ebe768d6ef5493098119c2e6b4796239d53e5ed7b122b206a5", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "/docs/18/libpq-envars.html", "file": "libpq-envars.html", "label": "18.6 English manual \u00b7 libpq-envars.html", "anchor": "", "sha256": "d64db73f3d48127bb984a5f775e77b7bcca2ba4bd218333cf24a45fcdd7c4363"}, {"url": "/docs/18/libpq-pgservice.html", "file": "libpq-pgservice.html", "label": "18.6 English manual \u00b7 libpq-pgservice.html", "anchor": "", "sha256": "6035a3f0ee1d0fd80db5bf58834390b884eecd23206659bdf6f07560deea5aa7"}], "sections": [{"title": "Default resolution and service-file precedence", "paragraphs": ["The following environment variables can be used to select default connection parameter values, which will be used by PQconnectdb , PQsetdbLogin and PQsetdb if no value is directly specified by the calling code. These are useful to avoid hard-coding database connection information into simple client applications, for example.", "Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . On Microsoft Windows, it is named %APPDATA%\\postgresql\\.pg_service.conf (where %APPDATA% refers to the Application Data subdirectory in the user's profile). A different file name can be specified by setting the environment variable PGSERVICEFILE . The system-wide file is named pg_service.conf . By default it is sought in the etc directory of the PostgreSQL installation (use pg_config --sysconfdir to identify this directory precisely). Another directory, but not a different file name, can be specified by setting the environment variable PGSYSCONFDIR .", "Connection parameters obtained from a service file are combined with parameters obtained from other sources. A service file setting overrides the corresponding environment variable, and in turn can be overridden by a value given directly in the connection string. For example, using the above service file, a connection string service=mydb port=5434 will use host somehost , port 5434 , user admin , and other parameters as set by environment variables or built-in defaults."]}, {"title": "Environment variable evidence", "paragraphs": ["PGMINPROTOCOLVERSION behaves the same as the min_protocol_version connection parameter."]}], "signature": "min_protocol_version", "documented": true, "description": ["Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed."], "environment": [{"name": "PGMINPROTOCOLVERSION", "source_url": "/docs/18/libpq-envars.html", "description": "PGMINPROTOCOLVERSION behaves the same as the min_protocol_version connection parameter."}], "manual_html": "<div><dl class=\"variablelist\"><dt id=\"LIBPQ-CONNECT-MIN-PROTOCOL-VERSION\"><span class=\"term\"><code class=\"literal\">min_protocol_version</code></span> </dt><dd>\n<p>Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the <span class=\"productname\">PostgreSQL</span> protocol supported by libpq, which currently means <code class=\"literal\">3.0</code>. If the server does not support at least this protocol version the connection will be closed.</p>\n<p>The current supported values are <code class=\"literal\">3.0</code>, <code class=\"literal\">3.2</code>, and <code class=\"literal\">latest</code>. The <code class=\"literal\">latest</code> value is equivalent to the latest protocol version supported by the libpq version being used, which is currently <code class=\"literal\">3.2</code>.</p>\n</dd></dl></div>", "manual_path": "libpq-connect.html#LIBPQ-CONNECT-MIN-PROTOCOL-VERSION", "source_option": {"keyword": "min_protocol_version", "declaration": "\"min_protocol_version\", \"PGMINPROTOCOLVERSION\", NULL, NULL, \"Min-Protocol-Version\", \"\", 6, offsetof(struct pg_conn, min_protocol_version)", "environment": "PGMINPROTOCOLVERSION", "source_notes": [], "compiled_default_expression": "NULL"}, "comparison_data": {"keyword": "min_protocol_version", "definition": "Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed. The current supported values are 3.0 , 3.2 , and latest . The latest value is equivalent to the latest protocol version supported by the libpq version being used, which is currently 3.2 .", "documented": true, "environment": "PGMINPROTOCOLVERSION", "default_evidence": ["Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed."], "compiled_default_expression": "NULL"}, "comparison_hash": "935c998892c3632ad1e984dcf59a08b726671ddc4efa152ef1d02f7922b2cba6", "default_evidence": ["Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed."], "precedence_evidence": ["The following environment variables can be used to select default connection parameter values, which will be used by PQconnectdb , PQsetdbLogin and PQsetdb if no value is directly specified by the calling code. These are useful to avoid hard-coding database connection information into simple client applications, for example.", "Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . On Microsoft Windows, it is named %APPDATA%\\postgresql\\.pg_service.conf (where %APPDATA% refers to the Application Data subdirectory in the user's profile). A different file name can be specified by setting the environment variable PGSERVICEFILE . The system-wide file is named pg_service.conf . By default it is sought in the etc directory of the PostgreSQL installation (use pg_config --sysconfdir to identify this directory precisely). Another directory, but not a different file name, can be specified by setting the environment variable PGSYSCONFDIR .", "Connection parameters obtained from a service file are combined with parameters obtained from other sources. A service file setting overrides the corresponding environment variable, and in turn can be overridden by a value given directly in the connection string. For example, using the above service file, a connection string service=mydb port=5434 will use host somehost , port 5434 , user admin , and other parameters as set by environment variables or built-in defaults."]}, "comparison": {"left": "17", "right": "18", "status": "added", "diff": "--- PostgreSQL 17\n+++ PostgreSQL 18\n@@ -1 +1,10 @@\n-Not recorded in this version\n+{\n+  \"compiled_default_expression\": \"NULL\",\n+  \"default_evidence\": [\n+    \"Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed.\"\n+  ],\n+  \"definition\": \"Specifies the minimum protocol version to allow for the connection. The default is to allow any version of the PostgreSQL protocol supported by libpq, which currently means 3.0 . If the server does not support at least this protocol version the connection will be closed. The current supported values are 3.0 , 3.2 , and latest . The latest value is equivalent to the latest protocol version supported by the libpq version being used, which is currently 3.2 .\",\n+  \"documented\": true,\n+  \"environment\": \"PGMINPROTOCOLVERSION\",\n+  \"keyword\": \"min_protocol_version\"\n+}"}}