Tracking6 min read
Session replay
Session replay records a visual playback of a visitor's session (DOM changes, mouse movement, scrolling) without ever recording what they typed into a sensitive field.
Turning it on
Session replay is a dashboard setting, not a snippet attribute: go to Settings on your site and switch it on. A sample-rate slider next to the toggle controls what fraction of new sessions get recorded, from 0% to 100%.
New page loads pick up the change on their very next pageview. A tab that's already open when you flip the toggle won't start recording until it reloads.
Sampling
The dice are rolled once per page load, when the tracker gets its first response from the collect endpoint. In a single-page app that is the whole visit, so the session records end to end. On a traditional multi-page site each full page load is its own roll, so at a sample rate below 100% a visit can be recorded on one page and not the next, and a session's playback can have gaps in it.
If you want whole multi-page journeys rather than fragments, set the sample rate to 100% and use it for a short window rather than leaving a partial rate on permanently.
Masking
By default, every form input's value is masked in the recording: you'll see that a field was typed into, never what was typed. This is controlled by the data-mask-input script attribute (default 1, meaning "mask everything"). If you set it to 0 to record values in ordinary text fields, password and email inputs are still always masked. That floor doesn't move.
The replay library itself is served from your own tracking domain rather than a third-party CDN, so it isn't blocked by a Content-Security-Policy that only allowlists Mrkr's own host.
Where recordings live, and for how long
Each recorded session is stored as an object in object storage (not a database table), indexed by an entry that carries the session's visitor, device, browser, duration, and page count for the Replay list. Recordings are retained for 90 days, regardless of your plan's general data-retention window: a Business plan's 3-year retention for aggregate analytics does not extend to replay recordings.
Testing the pipeline
Settings includes a "Send a test event" button that posts a small synthetic recording straight through the replay pipeline, so you can confirm storage and indexing are wired up correctly without waiting for real traffic to arrive.