JavaScript Payload Analyzer
SiteTend JavaScript Payload
Estimate measurable JavaScript weight and find blocking, duplicate, third-party, legacy, and main-thread risk indicators.
Paste JavaScript resource information
Add HTML, script elements, resource lists, or build output with sizes.
Review payload risks
Start with blocking scripts, large payloads, and long-task risk.
Your analysis will appear here
Paste resource information and select Analyze JavaScript.
How to improve
Reduce code before rearranging bundles
Remove unused features, delay non-essential work, control third parties, and profile execution on representative mobile hardware. Treat request count and bundle structure as means to a measured user-experience outcome.
Questions
JavaScript Payload Analyzer FAQ
How does the analyzer estimate JavaScript payload?
It totals inline code and sizes explicitly included in pasted build output or markup. Resources without a stated size remain unmeasured.
Which script loading mode should I use?
Use defer for ordered scripts, async for independent scripts, and module scripts for modern module loading. Verify dependencies whenever execution timing changes.
Can a filename prove that framework code is unused?
No. Framework, runtime, and polyfill findings are investigation prompts. Confirm them with bundle composition and code-coverage tools.
Does SiteTend fetch JavaScript resources?
No. Version 1 analyzes only the content pasted into your browser.
Apply the result
From finding to verified fix
Interpret the finding
Use size and loading warnings to choose what to profile first; they do not prove that a script is unused or slow at runtime.
Common causes to inspect
- Duplicate libraries
- Large application bundles on simple pages
- Third-party scripts loaded before user intent
Practical next steps
- Inventory first- and third-party scripts
- Profile execution and coverage
- Remove, split, or defer one verified cost at a time
What this check cannot prove
Markup estimates cannot download bundles, inspect source maps, measure execution, or observe long tasks.