Developer Guides
In-depth, source-checked articles for working developers. Each guide is reviewed against IETF RFCs, W3C/WHATWG specs, MDN Web Docs, and official project repositories before publication.
JWT Anatomy: Header, Payload, and Signature Explained
RFC 7519 claims, RFC 7515 signatures, the alg=none vulnerability, refresh tokens, and JWT vs session cookies — for engineers shipping auth in 2026.
Auth·10 min read·DevToolNow Editorial TeamRegex Lookahead and Lookbehind: When You Actually Need Them
When the four lookaround forms earn their complexity, when capture groups are simpler, and what the ES2018 support story really looks like in 2026.
Regex·10 min read·DevToolNow Editorial TeamCron Expression Cheatsheet: Every Field Explained
Standard 5-field cron, Quartz 6-field cron, the special characters that vary by dialect, DST gotchas, and when systemd timers replace cron entirely.
DevOps·10 min read·DevToolNow Editorial TeamHash Algorithms Compared: MD5, SHA-1, SHA-256, bcrypt, and Argon2
Where MD5 and SHA-1 still earn their keep, why SHA-256 is the general-purpose default, and why password hashing needs Argon2 or bcrypt — not a faster hash.
Crypto·10 min read·DevToolNow Editorial TeamColor Formats in 2026: HEX, RGB, HSL, and Why OKLCH Matters
Why OKLCH is becoming the design-token default — and what HEX, RGB, HSL, HWB, and LCH still do well in production CSS.
CSS·10 min read·DevToolNow Editorial TeamUnix Timestamp vs ISO 8601: Picking a Date Format for APIs
Unix epoch seconds vs ISO 8601 strings — what RFC 3339 actually requires, why timezone offsets matter, when the Year 2038 problem still bites, and what to send over the wire.
Date·10 min read·DevToolNow Editorial TeamURL Encoding Explained: When to Use encodeURI vs encodeURIComponent
RFC 3986 percent-encoding, the difference between encodeURI and encodeURIComponent, why URLSearchParams is usually the right answer, and how to avoid double-encoding bugs.
URL·10 min read·DevToolNow Editorial TeamUUID v4 vs UUID v7 vs ULID: Choosing IDs for Production Systems (2026)
RFC 9562 added UUID v7 as a time-ordered alternative to v4. Here's when to use each format — including ULID and NanoID — for primary keys, distributed systems, and public-facing APIs.
Identifiers·9 min read·DevToolNow Editorial Team