Developer Tutorials & Tool Guides
Most developer tasks look trivial until an edge case appears: a JSON number with a leading zero, a cron expression that fires at the wrong hour, a diff that hides a semantic change. These tutorials cover the details.
The tutorials are grouped by the bug they prevent. Encoding and data shaping covers Base64 against Base64URL and data URIs, JSON formatted against RFC 8259 including the number and escape rules that parsers disagree about, and CSV that has to survive quotes and embedded newlines. Text utilities covers regular expressions with a live tester, cron expressions with the next fire times in your own timezone, and diffs that separate a formatting change from a semantic one.
Identifiers and timestamps form a group of their own, because UUID v4, v7 and ULID are a storage decision rather than a formatting one, and a Unix timestamp stays ambiguous until its unit and timezone are known. The smaller daily tasks are here too: colour conversion between hex, RGB and HSL, Markdown tables, image compression that runs in the browser, and CSS minification you can inspect before it ships.
Compress an Image Without Uploading It
Most free compressors upload the file before they shrink it. This workflow keeps the image on your device and still gets it small enough to send.
Compress an Image for Email
Most email rejections come from dimensions, not quality. Resize first, keep JPEG for photos, and check the text that must stay readable.
CSS Minifier Guide: Shrink Stylesheets
CSS is mostly whitespace and comments by weight. A minifier removes both — and a good one knows exactly what must survive.
Certificate Decoder Guide: Read X.509 Details
Every TLS handshake starts with a certificate. Decode the fields that matter: subject, issuer, validity, public key, and fingerprints — locally.
CSV to JSON Converter Guide
CSV looks simple until a field contains a comma, a newline, or a leading equals sign. Learn the RFC 4180 rules and convert data without losing anything.
Color Converter Guide: HEX, RGB, HSL
HEX, RGB, and HSL are three views of the same color. Know what each format represents, when alpha matters, and how to check contrast before you ship.
Cron Expression Guide: Five Fields, Next Runs
A cron expression is five fields that look obvious until one of them is wrong. Learn the syntax, the day-of-week trap, and how to preview the next runs before you deploy.
Regex Tester Guide: Test Patterns Locally
Most regex failures are visible the moment you see the matches: wrong flags, greedy quantifiers, or a group you never intended. Test locally and read the actual matches before blaming the pattern.
Batch Image Compression: A Local Workflow Guide
Email limits, upload forms, and page speed all punish oversized images. Compress a whole folder in your browser - no upload, no account, no quality guessing.
JSON Diff vs Text Diff: Which to Use
A text diff on JSON screams about reordered keys and reformatting. A semantic JSON diff tells you what actually changed. Here is when to use each.
Decode JWT From Error Logs
A failed request usually leaves the token in a log line. Decode it locally to see exp, iat, iss, and aud before touching any code - and never paste it into a random decoder.
Markdown Tables: How to Create and Format Them
Tables are a GFM extension, not part of original Markdown. Three lines of syntax cover most cases; alignment is one colon in the separator row.
Base64 Data URIs: Use and Optimize
A data URI removes one HTTP request for a tiny icon and bloats the page for anything larger. The line between the two sits somewhere around a few kilobytes.
UUID v7 vs ULID: Sortable IDs Compared
Both fix the same problem: random IDs scatter index inserts, time-ordered IDs do not. UUID v7 fits existing UUID parsing; ULID is a compact Base32 string. Pick what your stack already understands.
JWT Expiration & Clock Skew: exp, iat, nbf
When a JWT fails validation, the claims usually say why. exp, iat, and nbf are plain Unix seconds, so you can decode them and compare against the server clock before touching any code.
Base64 vs Base64URL: Key Differences
Standard Base64 breaks inside URLs: + reads as a space, / splits paths. Base64URL swaps in - and _, which is why JWT segments use it. The difference is small, but it decides whether your data round-trips.
UUID v7 Generator: Time-Ordered IDs
v4 scatters inserts across the key space; v7 keeps them near the current time. The visible timestamp is the trade-off, and it matters if your IDs are user-visible.
Unix Timestamp: A Developer's Guide
A mismatch between seconds and milliseconds in timestamp handling can cause data integrity issues scheduling failures and security vulnerabilities in production systems.
UUID Versions Explained: A Complete Guide
Understanding UUID versions, their use cases, and how to generate them securely in the browser.
Code Review with Diff Tools: Best Practices
A diff is a line-by-line comparison of two versions of a file. In code review, read the added logic first: whitespace and reordering are noise, while a changed operator or a flipped condition is the bug.
JSON Formatter: A Developer's Guide to RFC 8259
Most online JSON formatters log every piece of data that passes through their servers. For developers handling sensitive API responses, this creates a significant security risk.