JSON Size Analyzer - Free Online Tool

Measure original, pretty, minified and gzip sizes. Spot the largest fields and optimize your payloads.

Original
0 B
Input bytes (UTF-8)
Pretty
0 B
0.0% vs original
Minified
0 B
0.0% vs original
Gzip
—
Click calculate
JSON Input
Paste JSON above to analyze size by property.
  • Tip: Remove unused fields or shorten keys to reduce size.
  • Minify JSON before sending. Gzip/Brotli provide further reductions.
  • Keep numbers compact; avoid unnecessary string formatting.

Optimize JSON Payloads for Web Vitals

Understand where your JSON size comes from. This analyzer highlights the biggest contributors so you can trim bytes, cut network time, and deliver faster experiences.

Measure what matters
Original, Pretty, Minified, and Gzip estimates
Spot heavy properties
Size-by-property view with aggregation
Worker-powered
Smooth UI on large inputs via Web Worker
SEO-friendly
Server content with minimal client JS

Best Practices

  • Remove unused fields and redundant nesting.
  • Prefer numbers/booleans over strings.
  • Shorten repetitive keys or map keys client-side.
  • Normalize arrays to avoid deep duplication.
  • Always serve compressed (Gzip/Brotli).

FAQ

How is size calculated?
UTF‑8 byte length with property name overhead considered.
Why aggregate arrays?
Highlights cost across items instead of per-index noise.
What about gzip?
Use Calculate Gzip Size for a quick estimate via browser APIs.
Does it block UI?
Heavy work runs in a Web Worker to keep the UI smooth.