# ssl

> ssl is the PostgreSQL setting that controls whether PostgreSQL enables SSL connections.
---

> [!NOTE]
> **Fact — official short description:** “Enables SSL connections.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `bool` | Upstream pg_settings type |
| Context | `sighup` | Takes effect after configuration reload |
| Unit | — | Raw unit |
| Range | — | Raw limits in the last observed version |
| Enum values | — | — for non-enum types |
| Category | Connections and Authentication / SSL | Upstream classification |
| Latest boot value | `off` | off |
{.fields meta="-"}

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG9.0 (research boundary) |
| Present in | PG9.0–19 Beta 3 |
| Removed in | No |
| Introduction commit | Not asserted: predates the PG9.0 research boundary |
| Commit date | — |
| Discussion | — |

## Default history {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG9.0–19 Beta 3 | `off` | — | off |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

ssl enables SSL connections. Turning it on makes TLS listeners available when certificate and key material are valid; pg_hba.conf hostssl rules are what require TLS for selected clients.

ssl is a SIGHUP-context setting: a configuration reload activates the new server value without a restart; subsequent operations that consult it use the refreshed value. Existing TLS sessions are not renegotiated.

It participates in the TLS context used for new handshakes. ssl enables transport, pg_hba.conf decides which connection classes require it, and the certificate, key, CA, revocation, protocol, and cipher settings must form one valid policy.

## Tuning advice {#tuning-advice}

> [!TIP]
> **Advice.** These are workload-specific starting points and must be validated with measurements.

| Workload | Guidance |
| --- | --- |
| OLTP | Treat ssl as transport-security policy rather than a performance knob. Follow the organization's TLS baseline and test certificate rotation, reload, and every client class. |
| OLAP | Use the same TLS floor for analytical traffic; benchmark only after correctness because bulk transfer may expose CPU cost but is not a reason to accept obsolete protocols. |
| Small nodes | Keep ssl simple and secure, using managed certificates and library defaults reviewed for the installed OpenSSL version. Rehearse renewal before expiry. |
{.full-width}

## Pigsty {#pigsty}

Values use the fixed 8-vCPU, 32-GiB, 100-GiB SSD fixture and render the current Pigsty templates for PG19 Beta 3; this does not assert current Pigsty support for that historical or beta release.

| Template | Effective value | Versus upstream boot | Source expression |
| --- | --- | --- | --- |
| OLTP | `on` | different | `'on'` |
| OLAP | `on` | different | `'on'` |
| CRIT | `on` | different | `'on'` |
| TINY | `on` | different | `'on'` |
{.full-width}

> [!CAUTION]
> **Advice — pending human review.** Fact from the current Pigsty template projection: OLTP: PG9.0–19 Beta 3 = on (dcs); OLAP: PG9.0–19 Beta 3 = on (dcs); CRIT: PG9.0–19 Beta 3 = on (dcs); TINY: PG9.0–19 Beta 3 = on (dcs). Advice, pending human review — Editorial inference: All templates enable TLS so certificate-based encrypted transport is available as a uniform baseline; pg_hba.conf must still require it where policy demands.

## Common pitfalls {#common-pitfalls}

- Editing ssl without reloading configuration and verifying the effective value and subsequent behavior.
- Updating only one TLS file or policy knob and leaving an invalid chain, unreadable key, or incompatible protocol set.
- Assuming a reload renegotiates existing sessions; TLS policy changes affect new handshakes.
- Changing ssl globally without a rollback plan and a client or operational compatibility test.

## Related parameters {#related-parameters}

[`ssl_cert_file`](/parameters/ssl-cert-file/) · [`ssl_key_file`](/parameters/ssl-key-file/) · [`ssl_ca_file`](/parameters/ssl-ca-file/) · [`ssl_crl_file`](/parameters/ssl-crl-file/) · [`ssl_min_protocol_version`](/parameters/ssl-min-protocol-version/)

## References {#references}

- [PostgreSQL 19 Beta 3 — ssl](https://www.postgresql.org/docs/19/runtime-config-connection.html#GUC-SSL)
- [PostgreSQL 19 release notes](https://www.postgresql.org/docs/19/release-19.html)
- [Machine-readable GUC export](/data/guc.jsonl)