# Developer Tools

> One page from jmrp.io, published as markdown. Index: https://jmrp.io/llms.txt

Canonical: https://jmrp.io/tools/categories/developer/
Language: en
Alternate: https://jmrp.io/es/tools/categories/developer/index.md
Updated: 2026-09-03
License: https://jmrp.io/license/
Category: developer

Free online developer utilities — Base64 encoder, regex tester, cron expression builder, Unix timestamp converter, and color contrast checker.
Build-Date: 2026-09-06

The small conversions that interrupt real work: decoding a Base64 blob, testing a regex against sample text, writing a cron expression you can trust, turning a Unix timestamp into a date, or checking a color pair against WCAG. Each one does its job without an account, an upload, or a network request.

- [Base64 Encoder / Decoder](https://jmrp.io/tools/base64-encoder/): Encode and decode Base64, Base64URL, URL encoding, hex, and HTML entities. File support for images and documents. Runs client-side. ([markdown](https://jmrp.io/tools/base64-encoder/index.md))
- [Color Contrast Checker](https://jmrp.io/tools/color-contrast-checker/): Check color contrast ratios for WCAG 2.2 AA and AAA compliance with APCA support, color blindness simulation, and auto-fix suggestions. Runs client-side. ([markdown](https://jmrp.io/tools/color-contrast-checker/index.md))
- [Cron Expression Builder](https://jmrp.io/tools/cron-builder/): Visual cron expression builder with interactive field selectors, presets, next execution preview, and crontab output. Runs client-side. ([markdown](https://jmrp.io/tools/cron-builder/index.md))
- [Regex Tester](https://jmrp.io/tools/regex-tester/): Test regular expressions with real-time match highlighting, capture groups, replace mode, and common pattern presets. Runs in your browser. ([markdown](https://jmrp.io/tools/regex-tester/index.md))
- [Unix Timestamp to Date Converter](https://jmrp.io/tools/timestamp-converter/): A Unix timestamp counts seconds since 1970-01-01 UTC. Convert one to a date and back, seconds or milliseconds, in 11 time zones — all in your browser. ([markdown](https://jmrp.io/tools/timestamp-converter/index.md))

## All categories

- [Security Tools](https://jmrp.io/tools/categories/security/) ([markdown](https://jmrp.io/tools/categories/security/index.md))
- [Network & Server Tools](https://jmrp.io/tools/categories/network/) ([markdown](https://jmrp.io/tools/categories/network/index.md))
- [Embedded & Industrial Tools](https://jmrp.io/tools/categories/embedded/) ([markdown](https://jmrp.io/tools/categories/embedded/index.md))
- [MikroTik Tools](https://jmrp.io/tools/categories/mikrotik/) ([markdown](https://jmrp.io/tools/categories/mikrotik/index.md))