POLPROG JSON Formatter
What POLPROG JSON Formatter is
POLPROG JSON Formatter is a free web tool for formatting, validating, inspecting, and comparing JSON. It can indent documents with two or four spaces or tabs, minify them, and sort object keys in either A–Z or Z–A order. It also converts JSON to YAML, a TypeScript interface, or CSV. When validation finds a problem, it reports the line, column, character offset, and cause; it can also flag duplicate keys and large integers that JavaScript may not preserve precisely.
For comparison, its semantic diff disregards indentation, line endings, and object key order, but treats arrays as ordered sequences. A tree view provides copyable paths and values, and search can locate keys or values. The page says JSON is processed locally in the browser: pasted or dropped documents are not uploaded to POLPROG servers. It retains the selected indentation between visits, while document content is not saved to storage or the address bar. Documents can be up to 5 MiB. Syntax highlighting turns off above 300 KiB, and detailed diff may stop early for very large trees. The tool requires JavaScript and does not validate JSON Schema or repair broken documents.
Who it suits
It suits developers and others who need to inspect API responses, check webhook payloads, compare configuration versions, or turn sample JSON responses into TypeScript interfaces. It runs in a JavaScript-enabled browser and does not require registration.
What it does well
- Formats with two spaces, four spaces, or tabs, and can minify JSON.
- Converts JSON to YAML, TypeScript interfaces, or CSV.
- Validation reports an error’s location and cause.
- Semantic diff ignores formatting and object key order.
- Processes documents locally in the browser, according to the page.
What to know first
- Documents are capped at 5 MiB.
- Syntax highlighting turns off above 300 KiB.
- It does not validate JSON Schema or repair broken documents.
Limits
The free tool accepts documents up to 5 MiB. Syntax highlighting switches off above 300 KiB, and detailed diff may stop early on very large trees.
Plans
| Plan | Billed and limits | Price |
|---|---|---|
| Free | Free to use · no registration | Free |
As polprog.pl lists them, read 7 Oct 2026. The maker's own page has the final word.
Getting started
- Open the POLPROG JSON Formatter website in a browser.
- Ensure JavaScript is enabled.
- Use the free tool without registration.
Verdict
Choose POLPROG JSON Formatter for browser-based JSON formatting, validation, conversion, tree inspection, and semantic comparison. Its local processing and no-registration free plan suit quick document work; look elsewhere if you need JSON Schema validation or automatic repair.
Questions
How much does POLPROG JSON Formatter cost?
The Free plan costs nothing and is free to use without registration.
Is there a free trial?
No. The listed plan is free to use, and there is no free trial.
Which platforms does it support?
It is available on the web and requires JavaScript in the browser.
Does it validate JSON Schema?
No. JSON Schema validation is not available.
Does it compare JSON documents?
Yes. Its semantic diff ignores indentation, line endings, and object key order, while comparing arrays in order.
Who makes the tool?
POLPROG describes itself as a Polish technology company founded by Damian Skrzyński and based in Warsaw, Poland.
Facts from POLPROG JSON Formatter's own pages
- Comparison
- Its semantic diff ignores indentation, line endings and object key order, while comparing arrays as ordered sequences. · polprog.pl, 7 Oct 2026
- Conversion
- It can convert JSON to YAML, a TypeScript interface or CSV. · polprog.pl, 7 Oct 2026
- File limit
- Documents are capped at 5 MiB; syntax highlighting switches off above 300 KiB and detailed diff may stop early on very large trees. · polprog.pl, 7 Oct 2026
- Formatting
- It can format JSON with two spaces, four spaces or tabs, and can minify it. · polprog.pl, 7 Oct 2026
- Headquarters
- Warsaw, Poland · polprog.pl, 28 Sept 2026
- Intended use
- The page describes use cases including reading API responses, checking webhook payloads, comparing configuration versions and turning sample responses into TypeScript interfaces. · polprog.pl, 7 Oct 2026
- Local storage
- The page says the only setting retained between visits is the selected indentation, and document content is not written to storage or the address bar. · polprog.pl, 7 Oct 2026
- Maker
- POLPROG describes itself as a Polish technology company founded by Damian Skrzyński and says it is based in Warsaw, Poland. · polprog.pl, 7 Oct 2026
- Privacy
- JSON processing runs locally in the browser and the page says pasted or dropped documents are never uploaded to POLPROG servers. · polprog.pl, 7 Oct 2026
- Purpose
- The browser-based tool formats, validates, inspects and compares JSON. · polprog.pl, 7 Oct 2026
- Requirements
- The workspace runs in the browser and requires JavaScript. · polprog.pl, 7 Oct 2026
- Scope limit
- The tool does not validate JSON Schema or repair broken documents. · polprog.pl, 7 Oct 2026
- Sorting
- It can sort JSON keys A–Z or Z–A. · polprog.pl, 7 Oct 2026
- Tree and search
- The tool provides a tree view with copyable paths and values, plus search for keys or values. · polprog.pl, 7 Oct 2026
- Validation
- Validation reports the error line, column, character offset and cause, and can flag duplicate keys and large integers that lose precision in JavaScript. · polprog.pl, 7 Oct 2026
Where POLPROG JSON Formatter stands on Freedom251
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