What is session replay?
Session replay is a technique that reconstructs a user's browser session as a replayable recording of DOM changes and interactions, letting you watch exactly what the user saw and did when a bug or confusing experience occurred.
Definition
Session replay (also called session recording) captures what happens in a user's browser and lets you play it back later like a video. Crucially, most modern session replay is not a screen video at all — it records the structure of the page (the DOM) and every change to it, plus user interactions like clicks, scrolls, and input events. On playback, the tool re-renders those DOM mutations in sequence to recreate exactly what the user experienced.
Recording the DOM rather than pixels makes replays lightweight, searchable, and inspectable — you can see the actual elements, console errors, and network activity, not just an image. Because this data can contain sensitive personal information, privacy masking is a core part of session replay: text inputs, specific fields, or whole elements can be blocked or obfuscated at capture time so they never leave the user's browser.
How session replay works
Session replay records a structured stream of changes, then reconstructs the experience for debugging — with privacy built in.
DOM snapshots & mutations
An initial snapshot of the page plus an incremental stream of every DOM change, so the page state can be perfectly reconstructed at any moment.
User interactions
Clicks, mouse movement, scrolling, and keypresses are recorded as timed events so playback shows not just the screen but the user's behavior.
Privacy masking
Sensitive inputs and elements are masked or excluded at capture time, so passwords, payment details, and PII are never recorded or transmitted.
Error correlation
Replays linked to captured errors let you watch the exact moments and steps that led up to an exception, turning a stack trace into a story.
Why session replay matters
Some bugs are nearly impossible to reproduce from a stack trace alone — they depend on an unusual sequence of clicks, a specific viewport, or a flow the user took that nobody anticipated. Session replay removes the guesswork: instead of asking a user to describe what they did, you watch it. The minutes you'd spend trying to reproduce an issue collapse into a single playback.
Beyond debugging, replay reveals UX friction — rage clicks, dead ends, abandoned forms — that aggregate analytics can only hint at. The trade-off is privacy: because you're recording real user sessions, masking sensitive data is not optional, which is why responsible session replay defaults to blocking inputs and PII unless explicitly allowed.
Session replay with AllStak
AllStak offers web session replay that reconstructs a user's browser session from DOM mutations and interactions, with privacy masking for sensitive inputs. Because replay lives in the same platform as your error tracking, you can jump straight from a captured exception to the recording of the session that produced it — and see exactly what the user did before it broke.
Frequently asked questions
What is session replay?
It is a technique that reconstructs a user's browser session — by recording DOM changes and interactions — so you can replay exactly what they saw and did, most often to debug an issue.
Is session replay a video recording?
Usually not. Most tools record the DOM and its mutations rather than pixels, then re-render them on playback. This is lighter, searchable, and lets you inspect real elements, console errors, and network activity.
How does session replay protect user privacy?
Through masking: sensitive inputs, fields, and elements are blocked or obfuscated at capture time so passwords, payment details, and personal data are never recorded or sent to the server.
How is session replay different from screen recording?
Screen recording captures pixels as video; session replay captures the structured DOM and events, which is more efficient and far more useful for debugging because you can inspect the actual page.
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Capabilities
By framework
Watch the session behind the bug
Reconstruct user sessions with privacy masking and jump from an error straight to the replay that caused it.