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Format, encode, decode and convert in the browser

Developers lose minutes every day to small chores: pretty-printing an API response, decoding a token to check its expiry, testing a regular expression, converting a CSV export to JSON or generating a few UUIDs for test data. These free developer tools handle those chores in a browser tab, with no install and no account. The JSON formatter validates and beautifies with exact error locations, the regex tester highlights matches live, and the JWT decoder shows a token’s header and claims and can verify its signature.

The collection also covers encoding (Base64, URL encoding, HTML entities and binary), hashing and IDs (MD5 and SHA hashes, UUID v4 and v7), data conversion between CSV, JSON, YAML, Markdown and HTML, formatting and minifying for SQL, HTML, CSS and JavaScript, and reference tools such as a cron expression builder, a chmod calculator for Unix file permissions and a list of HTTP status codes with causes and fixes.

Work data is often sensitive. Production JSON, customer records, signing secrets and access tokens should not be pasted into a site that sends them to a server. Every tool here processes your input locally in the browser, so it stays on your machine. That makes them practical for backend and frontend developers, QA testers, data analysts, DevOps engineers and students learning web development. The tools also work on a phone, which helps when you need to check a payload, a cron schedule or a timestamp away from your desk.

Base64, URL encoding or HTML entities?

All three turn text into a safer form, but for different destinations, and using the wrong one is a common bug.

• Base64 turns any bytes, including images and binary files, into 64 plain characters so they can travel inside JSON, email or a data URI. It makes data about a third larger and is not encryption.
• URL encoding, or percent-encoding, escapes characters such as spaces, ?, # and & so a value can sit safely inside a URL or query string. Use it for parameters, not for whole files.
• HTML entity encoding turns < and > into &lt; and &gt; so text displays as text on a web page instead of being read as markup. The HTML entity encoder also decodes named and numeric entities.
• Hashing is one-way. A SHA-256 hash proves two inputs are identical but cannot be reversed. For storing passwords, use a slow algorithm such as bcrypt, available in our security tools.

Data conversion and everyday tips

• Validate before you convert. Run JSON through the formatter first, because a trailing comma or a single-quoted key is the most common reason a conversion fails.
• Moving between spreadsheets and APIs? CSV to JSON detects numbers and booleans, and JSON to CSV flattens nested objects into columns that open in Excel or Google Sheets.
• Prefer UUID v7 for new database keys when you want IDs that sort by creation time; v4 is fully random. The UUID generator creates both in bulk.
• Read a cron schedule back in plain English before deploying it. The cron expression generator lists the next run times, so a wrong field stands out.
• A JWT payload is only Base64url-encoded, not encrypted. Never put secrets in it, and verify the signature before trusting any claim.