Privacy-first utilities for developers, sysadmins, and operators — format, convert, calculate, and play without sending tool data to a server.

Bidirectional conversion with validation, formatting, and tree view.

JavaScript (ECMAScript) RegExp — real-time matching, groups, breakdown, and cheat sheet.

Encode and decode Base64, URLs, and JWTs entirely in your browser.

Side-by-side and unified diffs for text, code, and JSON.

Live camelCase, PascalCase, snake_case, kebab-case, and more.

Paste a curl command and get fetch, axios, Python, Go, or Node.

Unix seconds/millis ↔ ISO 8601 ↔ human time, with timezone shifting and a live clock.

MD5, SHA-1, SHA-256, SHA-384, and SHA-512 over text or a dropped file, plus HMAC with a key.

Paste a JSON sample and get a TypeScript interface, Zod schema, Go struct, or JSON Schema.

Bin/oct/dec/hex conversion, two's complement, and live bitwise ops across bit widths.

Decompose a URL, edit params in a table, rebuild it, and encode/decode per field.

Hex / RGB / HSL / OKLCH conversion plus WCAG AA/AAA contrast pass-fail.

HTML entities, JSON, unicode \u, regex, CSV quoting, and shell single-quotes.

Network, broadcast, wildcard, usable range, and host counts.

Owner/group/public rwx plus setuid, setgid, and sticky — octal, symbolic, and chmod command.

Human-readable cron descriptions plus the next five run times.

Build and validate email authentication DNS records with lookup budgets and issue flags.

Expand, compress, and analyse IPv6 addresses with prefix math and address counts.

Searchable HTTP status codes and common TCP/UDP ports — keyboard-first.

Inspect event.key, code, keyCode, location, and modifiers live.

Bulk IDs with Spacebar regenerate. Fully client-side.

Turn plain text into terminal-ready FIGlet-style banners.

Scenario-based recovery commands for common Git disasters.

Cryptographically strong passwords and diceware-style passphrases with an entropy meter.

Add or extract VAT/GST at UK, EU, and worldwide rates. Net, tax, and gross in one pass.

Day rate ↔ hourly, weekly/monthly estimates, and simple UK take-home sketches.

Straight-line and declining-balance schedules — fully client-side.

Validate IBANs, extract bank/branch/account fields, and resolve SWIFT/BIC from a local directory.

Bulk invoice numbers and payment references with custom prefixes.

Paste two amount lists or CSV columns and find matches, misses, and diffs.

Compare two invoice-number lists and extract matches or missed entries.

Due dates from net 30/EOM with UK bank holidays, plus statutory late-payment interest.

Checksum and format validation for UK and EU VAT numbers — no VIES call required.

Self Assessment, corporation tax, and VAT filing dates from your year end or quarter.

Income tax (English & Scottish bands), employee NI, student loans, and pension relief.

Limited-company director sketches — salary, dividends, corporation tax, and personal tax.

19%/25% bands with marginal relief, associated companies, and instalment thresholds.

Payment breakdown, interest vs principal, and the impact of overpayments.

Normalise bank CSV exports into one date / description / amount format for reconcile tools.

HMRC approved mileage rates and simplified home-working expenses — fully client-side.

Convert between cost, sell price, margin %, and markup % without mixing the two up.

Turn an IBAN, amount, and reference into a scannable EPC payment QR code.

Play shareable PICO-8 / TIC-80 style browser games with global high scores.