Performance

How Instant Replay stays fast, and what happens on heavy pages.

Instant Replay keeps a short rolling buffer in your browser.

It’s designed to stay lightweight on normal pages.

On heavy pages, Screendesk can reduce or disable recording automatically.

How Instant Replay works (technical)

Instant Replay continuously records DOM changes (using rrweb-style snapshots and incremental updates).

Data is stored locally in memory and purged on a rolling window (about 2 minutes).

When you trigger Instant Replay, Screendesk turns that buffer into a replay of what happened.

What Screendesk does to stay fast

Screendesk reduces work in three main ways:

• Samples and throttles events instead of capturing everything.
• Uses checkpoints plus incremental updates instead of full snapshots all the time.
• Keeps strict per-tab limits and purges old data automatically.

Event sampling and throttling (defaults)

• Scroll events are throttled (about 150ms, or 500ms on heavier pages).
• Mouse moves are sampled rather than tracked continuously.
• Inputs capture the final value, not every keystroke.
• Non-essential events can be skipped (focus/blur/touch).

Snapshot strategy (defaults)

Full DOM snapshots are expensive.

Screendesk takes periodic checkpoint snapshots (about every 30 seconds) and records incremental changes in between.

What we strip or disable

To reduce payload size, Screendesk removes or disables some data:

• Script tags and HTML comments
• Favicon and meta tag noise (social/robots/verification)
• Font collection
• Canvas and cross-origin iframe recording

Per-tab memory limits (defaults)

Typical caps per tab:

• DOM snapshots: 15MB
• Console logs: 1MB
• Network requests: 1MB
• Total: ~20MB

Heavy page detection

Some sites update constantly.

Those pages can spike CPU and memory.

Screendesk monitors activity and can disable Instant Replay recording on “heavy” pages.

Common examples:

• Realtime dashboards
• Trading and crypto tickers
• Spreadsheet apps (Google Sheets, Excel Online)
• Animation-heavy landing pages

When Instant Replay is disabled on a heavy page, Screendesk can still capture console logs and network requests at a reduced rate.

Override or block websites

Use Website management to control where Instant Replay runs.

See Website management.

1

Force-enable a heavy site

Open Settings → Manage Websites.

Add the domain to Always Enabled Sites.

2

Block a site completely

Open Settings → Manage Websites.

Add the domain to Blocked Sites.

Priority order

Screendesk checks rules in this order:

1. Blocked Sites (always off)
2. Always Enabled Sites (always on)
3. Automatic heavy page detection
4. Default behavior