Is Mixpanel Session Replay JavaScript SDK Browser-Specific Regarding Tab Close Behavior?

·Apr 22, 2026 05:37 AM·

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I am implementing mixpanel session replay JavaScript SDK. I want to know if this is browser specific on tab close ? because when i closes the chrome it will flush the session but in safari, firefox and other browser it is not working as expected also it missed some session from the recording 🎫

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5 comments

· Sorted by Oldest

Mixpanel Support
APP
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Julianne B. has marked ticket #255 as closed.
Julianne Bozzini
APP
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Yes, this is expected due to browser limitations, not a bug in your implementation. Chrome handles visibilitychange/beforeunload and sendBeacon reliably on tab close; Safari and Firefox are much more aggressive about killing background tasks and canceling in-flight requests, so the final flush frequently doesn't go through. A few things worth checking:
SDK version: There was a known Safari bug where replay payloads were getting truncated due to a CompressionStream issue, fixed in a recent release. I'd recommend making sure you're on the latest version.
Network tab on close: open DevTools on Safari/Firefox and watch whether the outbound replay requests show as canceled when you close the tab. That'll confirm if it's flush-on-close specifically.
Short sessions may be getting dropped for falling below the minimum duration threshold, depending on the record_min_ms settings.
Sahar E.
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What is the maximum delay for a session to appear in Mixpanel after Session Replay flushes? I'd like to understand the end-to-end latency — from the moment Session Replay flushes the recorded data, how long can it take for the session to become visible in the Mixpanel dashboard? Is there any official SLA or expected time range for this? Julianne B.
Julianne Bozzini
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Let me double check with engineering there. Will let you know once I have more info!
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Julianne Bozzini
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We don't have formal SLAs for Session Replay ingestion. In normal conditions, once the SDK flushes the replay payload, you should typically see the session appear in Mixpanel within a few minutes. On occasion it can take longer, but it would be unusual if you're consistently seeing that behavior.
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