/diagnosing-missing-recordings

name: diagnosing-missing-recordings
description: >
  Diagnoses why a session recording is missing or was not captured.
  Use when a user asks why a session has no replay, why recordings aren't appearing,
  or wants to troubleshoot session replay capture issues for a specific session ID
  or across their project. Covers SDK diagnostic signals, project settings,
  sampling, triggers, ad blockers, and quota/billing scenarios.

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](./references/diagnostic-signals.md) 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](./references/diagnosis-logic.md) 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](./references/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 | |