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© 2026 ConverterHub. All tools are free and client-side.Made for developers who ship.

Free Online Developer Tools — in Your Browser

Format JSON, decode JWTs, encode Base64, convert Unix timestamps — paste and convert right here. No sign-up, no tracking, no server calls.

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All tools

9 tools · 100% free

Formatters

JSON Formatter & Validator
Beautify minified JSON, validate syntax, and debug errors instantly. Free online JSON parser that runs 100% in your browser for privacy.

Encoders

Base64 Encoder / Decoder
Convert text to Base64 or decode Base64 strings back to text. fast, client-side, and handles UTF-8 characters correctly.
URL Encoder / Decoder
Escape special characters in URLs (percent-encoding) or decode them back. Essential for debugging query parameters and API strings.

Converters

Timestamp to Date Converter
Free online tool to convert Unix timestamps (seconds & milliseconds) to human-readable dates. RFC 2822 & ISO 8601 formatting. Client-side only.
JSON to CSV Converter
Convert nested JSON arrays to CSV format for Excel or Google Sheets. flattens objects and handles headers automatically.

Dev Utilities

JWT Decoder (Debug Only)
Decode JSON Web Tokens (JWT) to inspect headers and payloads. Client-side only for security - no secret keys required.
UUID Generator (v4)
Generate secure, random UUIDs (Universally Unique Identifiers) version 4 locally in your browser. Bulk generation supported.
HTML Entity Escape / Unescape
Escape special characters to HTML entities (e.g. < to &lt;) or unescape them back. Prevent XSS and format code for display.

Text

Word & Character Counter
Count words, characters, sentences, and paragraphs in real-time. Includes reading time estimation. Perfect for essays, tweets, and SEO.

From the blog

Practical notes on the tools developers actually use.

All posts →
Jun 20, 2026 · 4 min read
How to format JSON in 2026: a developer’s practical guide
When working with JSON data, I often find myself dealing with large, unreadable blobs of text that make it difficult to understand the structure and content of the data. For instan
Jun 19, 2026 · 4 min read
How to decode a JWT: the safe way in 2026
When working with authentication systems, I often encounter JSON Web Tokens (JWTs) that need to be decoded and verified. A JWT is a compact, URL-safe means of representing claims t
Jun 18, 2026 · 5 min read
URL encoding: the rules every API consumer gets wrong
I've seen many cases where a simple API request fails due to incorrect URL encoding. For instance, when sending a GET request with a query parameter that contains special character

Frequently asked questions

Are these developer tools really free?+

Yes. Every tool on ConverterHub is free with no sign-up, no paywall, and no usage limits.

Is my data sent to a server?+

No. All conversions run entirely in your browser. Nothing you paste is transmitted to our servers.

Do the tools work offline?+

Once a tool page has loaded it typically keeps working without a network connection, because all processing happens in the browser.

Which tool should I use to decode a JWT?+

Use the JWT Decoder. It splits the token into header, payload and signature and shows expiry in a human-readable format. It never asks for your secret.