Back to Free Tools
FREE TOOLS
HTTP Precondition Evaluator
Evaluate supported conditional-request headers against supplied representation state.
Method, Representation exists, Current entity tag, Last-modified instant, Conditional request headers JSON
http-precondition-evaluator.json (complete report)
Browser only
Runs locally in your browser. Your files, pasted content and generated output are not uploaded. Reset clears this tool’s working data.
This tool needs JavaScript. If it does not load, refresh the page and try again.
How to use this tool
- Enter values using the examples, or choose a local file where requested. Follow the displayed supported input shapes and limits.
- Choose Calculate result and inspect the complete result.
- Download result to save the primary file. Where supplied, additional links save source files and the full JSON report. Reset restores examples and clears output.
Examples
Method: GET
Representation exists: true
Current entity tag: "abc"
Last-modified instant: 2026-10-22T00:00:00Z
Conditional request headers JSON: {"If-None-Match":"\"abc\""}
Limitations
- Evaluate RFC9110 If-Match,If-Unmodified-Since,If-None-Match,If-Modified-Since precedence for an otherwise eligible request against supplied state. Strong/weak ASCII ETags,GET/HEAD versus mutation; at most100 tags and65536 characters per conditional value. Current tag/date may be empty when unavailable. Valid negative outcomes report304/412; proceed leaves the normal status undecided. IMF-fixdate conditional dates only. Unknown/malformed header values refuse even if precedence would ignore them. No ranges,network or authorization.
- Text fields are limited to100,000 UTF16 units each and400,000 combined UTF8 bytes; file fields have their own displayed limits. Combined output is at most4MiB. Processing stops after30 seconds; tool-specific bounds may be tighter.
- Generated source is a downloadable result and is not executed here. Inspection does not establish remote behavior, trust or standards certification.
Related tools
No items found.