Best Free Online Developer Tools for Everyday Coding

Use the Unix Timestamp Converter to convert seconds or milliseconds to local time, UTC, and ISO 8601, or convert a selected date and time back to both timestamp units. The example 1700000000 seconds represents 2023-11-14T22:13:20.000Z; choose local time or UTC when entering a date.

The CSV Data Cleaner removes fully blank rows and duplicate full rows, trims surrounding whitespace, optionally fills blank values, and lets you choose columns for the downloaded CSV. It handles local files up to 5 MiB and previews up to 100 rows; review its cleaning rules before relying on the output.

Try a pattern in the JavaScript Regex Tester against representative sample text. It shows a match count and highlights full matches; it does not display individual capture-group values. Include non-matching and edge-case samples because a few successful examples do not prove a pattern is correct for every input.

The Markdown Previewer renders Markdown as you type and can copy the rendered HTML. Use the Base64 Converter to encode UTF-8 text or decode Base64 text; Base64 is not encryption. For a small image data URI, the Image to Base64 Converter reads an image up to 5 MiB in the browser.

Use the JWT Decoder to view a token's decoded header and payload. Decoding does not verify its signature or claims, so never trust the output as authentication and do not paste production tokens. The UUID v4 Generator creates up to 50 identifiers per batch for development and test data; UUIDs are not authentication tokens.

Before reusing output, check input limits, supported formats, and what the page sends to account history. Tool calculations may run locally in your browser while separate history or analytics requests still occur. Use synthetic or redacted examples for sensitive work, and validate important output in the application that will consume it.