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JSON Size Analyzer
Measure the byte size of every key in a JSON document and compare minified with pretty output.
Analyze a JSON payload
Minified: 0 bytes · Pretty: 0 bytes · Saving: 0%
Keys: 0 · Depth: 0 · Arrays:
0 · Biggest: —
How to use the JSON Size Analyzer
- Paste the JSON document you want to measure.
- Read the byte totals, depth and array counts for the payload.
- Check the sorted table to find the biggest keys, then copy the report.
Features
- Per-key byte size with a share of the whole document
- Table sorted from the biggest key down
- Depth, key count and array count at a glance
- Minified versus pretty printed size comparison
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Frequently Asked Questions
Common questions about the free online json size analyzer.
Paste the JSON, then read the table below the summary. It is sorted by byte size, so the
heaviest keys sit at the top with their share of the payload.
Each key is minified with JSON.stringify and measured as UTF-8 bytes, so multi-byte
characters such as accents count as more than one byte.
It compares the pretty printed size with the minified size and reports the percentage you
save by shipping minified JSON in production.
Depth is the deepest nesting level in the document. A flat object has a depth of one, and
every nested object or array adds a level.
Yes. A root array is broken down by index, so each element is measured and listed separately
in the size table.
The tool shows the parser message so you can fix the syntax. Nothing is uploaded, so you can
paste private payloads safely.
No. Parsing and measuring happen entirely in your browser, so the document never leaves your
device.
Yes. Find the heaviest keys, then trim, shorten or lazy load those fields to shrink the
response that your clients download.
The only real limit is the memory of your device. Documents with tens of thousands of keys
are measured in a moment.
Yes. It is completely free with no account, no sign-up and no limit on how many documents you
paste.
Last updated: October 10, 2026