JSON Size Estimator
Estimate the byte size of a JSON payload, and how much minifying would save.
How heavy is this payload
The size of a JSON payload matters for performance — a large API response is slower to transfer and parse, and on a mobile connection that adds up. This measures the byte size of your JSON, and shows how much smaller it would be minified, so you can gauge whether a payload is heavier than it needs to be.
Paste the JSON and see its size, formatted and minified.
Trimming a payload down
If a payload is bigger than you would like, the measurement points to the savings. Minifying — stripping the whitespace used for readability — is free and often meaningful. Beyond that, the real weight usually comes from sending more data than the client needs: verbose field names, deeply nested structure, or fields nobody uses. Seeing the size is the first step to deciding whether to minify, paginate, or slim the response. For anything served at scale, a lighter payload is a direct win for speed.
Frequently asked questions
What does it measure?
The byte size of your JSON, both formatted and minified, so you can see how much whitespace is costing.
How do I make a JSON payload smaller?
Minify it to strip whitespace, and beyond that send only the fields the client needs rather than everything.
Is my JSON uploaded?
No. The measurement happens in your browser.