posthog/diagnosing-missing-recordings

Diagnosing missing session recordings

When a user asks "why wasn't this session recorded?" or "why don't I have any recordings?", follow this workflow to systematically diagnose the cause.

Available tools

| Tool | Purpose | | --------------------------------------- | ----------------------------------------------------- | | posthog:execute-sql | Query session event properties for diagnostic signals | | posthog:session-recording-get | Check if a recording actually exists for the session | | posthog:query-session-recordings-list | Search for recordings matching criteria |

Diagnostic signals

The PostHog SDK emits diagnostic properties on every event that explain the recording state. See the diagnostic signals reference for the full list.

The key signals are:

• $has_recording — whether PostHog has a stored recording for this session
• $recording_status — SDK state: active, buffering, disabled, sampled, paused
• $session_recording_start_reason — why recording started or didn't
• $sdk_debug_recording_script_not_loaded — recorder script blocked (ad blocker)
• $sdk_debug_replay_*_trigger_status — trigger states (URL, event, linked flag)
• $replay_sample_rate — configured sample rate at capture time

Workflow

Step 1 — Check if the recording exists

If the user provides a session ID, first check whether a recording actually exists:

posthog:session-recording-get
{
  "id": "<session_id>"
}

If this returns data, the recording exists — the issue is likely UI/filtering, not capture. If it returns 404, proceed to diagnose why.

Step 2 — Query diagnostic signals from events

Query the most recent event for the session to get SDK diagnostic properties:

posthog:execute-sql
SELECT
    properties.$has_recording AS has_recording,
    properties.$recording_status AS recording_status,
    properties.$session_recording_start_reason AS start_reason,
    properties.$sdk_debug_recording_script_not_loaded AS script_not_loaded,
    properties.$sdk_debug_replay_url_trigger_status AS url_trigger,
    properties.$sdk_debug_replay_event_trigger_status AS event_trigger,
    properties.$sdk_debug_replay_linked_flag_trigger_status AS flag_trigger,
    properties.$replay_sample_rate AS sample_rate,
    properties.$sdk_debug_replay_internal_buffer_length AS buffer_length,
    properties.$sdk_debug_replay_flushed_size AS flushed_size,
    properties.$lib AS sdk_library,
    properties.$lib_version AS sdk_version
FROM events
WHERE $session_id = '<session_id>'
ORDER BY timestamp DESC
LIMIT 1

Step 3 — Diagnose the verdict

Use the diagnosis logic reference to interpret the signals. The verdicts in priority order:

1. Recording exists ($has_recording = true) — recording is captured, issue is elsewhere
2. Ad blocked (script) ($sdk_debug_recording_script_not_loaded = true) — browser extension blocking the recorder script from loading
3. Disabled ($recording_status = 'disabled') — replay turned off in settings or SDK config
4. Trigger pending (trigger statuses are trigger_pending, none matched) — recording gated on trigger that never fired
5. Sampled out ($session_recording_start_reason = 'sampled_out') — excluded by sample rate
6. Buffering empty ($recording_status = 'buffering', buffer length = 0, nothing flushed) — initialized but no snapshots produced
7. Flush blocked (buffer length climbs across events while flushed_size stays at 0) — snapshots are produced but the /s/ ingestion endpoint is blocked by an ad blocker or misconfigured reverse proxy. Detecting this requires querying the trend across the session's events — see example 3 in examples.md
8. Unknown — signals don't match a known pattern

Step 4 — Check project-level settings (if no session ID)

When the user asks about recordings missing project-wide (no specific session), query for recent sessions to check the pattern:

posthog:execute-sql
SELECT
    $session_id,
    properties.$recording_status AS recording_status,
    properties.$session_recording_start_reason AS start_reason,
    properties.$sdk_debug_recording_script_not_loaded AS script_not_loaded,
    properties.$replay_sample_rate AS sample_rate
FROM events
WHERE event = '$pageview'
    AND timestamp > now() - INTERVAL 1 DAY
GROUP BY
    $session_id,
    recording_status,
    start_reason,
    script_not_loaded,
    sample_rate
ORDER BY max(timestamp) DESC
LIMIT 10

Look for patterns:

• All disabled → replay is turned off in project settings
• All sampled_out with low sample rate → sample rate too aggressive
• All script_not_loaded → likely a CSP or deployment issue, not just one user's ad blocker
• Mix of statuses → per-session issue, dig into specifics

Step 5 — Provide actionable recommendations

Based on the verdict, recommend specific actions:

| Verdict | Recommendation | | --------------- | ------------------------------------------------------------------------------------------------------------------------------------- | | Ad blocked | User's browser extension is blocking rrweb. Suggest trying without ad blocker, or using a proxy/custom domain for the recorder script | | Disabled | Check project replay settings — recording may be turned off. Link to Settings > Session replay | | Trigger pending | The configured trigger (URL pattern, event, or feature flag) never matched. Review trigger configuration | | Sampled out | Increase the sample rate in project settings, or use a trigger to guarantee capture for important sessions | | Buffering empty | Page closed before first snapshot. Common with very short sessions or single-page navigations. Consider lowering minimum duration | | Unknown | Direct user to troubleshooting docs: https://posthog.com/docs/session-replay/troubleshooting |

Examples

See real-world diagnostic examples showing how signal combinations map to verdicts. Use these to calibrate your interpretation of query results.

Tips

• If $lib_version is very old, some diagnostic signals won't be present. Note this to the user — upgrading the SDK will provide better diagnostics.
• A session might have events but no recording if the recording was deleted due to retention. Check the session's timestamp against the project's retention period.
• If $has_recording is true but the user can't find it, check if it's filtered out by duration, activity threshold, or playlist filters.