Session replay

Session replay records what happened in the browser — DOM mutations, clicks, navigation, console — and plays it back next to the error it produced.

Setup

import * as Sentry from "@sentry/browser";

Sentry.init({
  dsn: "https://<public_key>@<your-errora-host>/<project_id>",
  integrations: [
    Sentry.replayIntegration({
      maskAllText: true,       // privacy defaults: on
      blockAllMedia: true,
      maskAllInputs: true,
    }),
  ],
  replaysSessionSampleRate: 0.1,   // 10% of all sessions
  replaysOnErrorSampleRate: 1.0,   // 100% of sessions that hit an error
});

Two sample rates, deliberately:

• replaysSessionSampleRate — ordinary browsing. Keep it low; every recorded session costs.
• replaysOnErrorSampleRate — sessions where an error happened. Keep this at 1.0: this is the recording you will actually want to watch.

Privacy

Replay records your users' screens, so treat it as sensitive by default:

Control	Effect
maskAllText: true	Text nodes are replaced with blocks
maskAllInputs: true	Input values never leave the browser
blockAllMedia: true	Images/video are not recorded
class="sentry-mask"	Mask one specific element
class="sentry-block"	Do not record the element at all
class="sentry-ignore"	Record the element but not interactions with it

Masking happens in the browser, before anything is sent. Turn masking off only for elements you have deliberately reviewed.

In the UI

Replays lists recorded sessions with user, duration, error count, browser and OS. Open one for:

• Playback of the rrweb recording with a timeline
• Visited pages during the session
• Errors raised in that session, linked to their issues
• Linked traces, when tracing is on

From an issue, the Replay panel jumps straight to the moment the error happened. From user feedback, a replay_id does the same.

API

GET /api/v1/projects/{project_id}/replays?stats_period=24h&limit=&offset=
GET /api/v1/projects/{project_id}/replays/{replay_id}
GET /api/v1/projects/{project_id}/replays/{replay_id}/events

Cost

Replays are metered as the Session Replay service, per recorded session — the most expensive unit in the price list. Sampling is your cost control; see Wallet.

Troubleshooting

Symptom	Cause / fix
No replays at all	replayIntegration() missing, or both sample rates are 0
Replays but no error linkage	The error was captured in a different session/tab, or replay started after the error
Blank/broken playback	Cross-origin stylesheets can't be inlined — serve CSS from your own origin or allow CORS
Recording is huge	Long sessions on heavy DOMs; lower replaysSessionSampleRate and block noisy widgets with sentry-block
Sensitive data visible	Masking was turned off somewhere — audit mask* options and per-element classes