95+ tools across the site
Free online tools for devs in one place
JSON, UUID, Base64, Regex, QR Code, text, dates, colors, QA workflows and automation
Tools for developer productivity
4DevTool centralizes free browser-based tools for developers in the UK: JSON, Base64, JWT, Regex, QR Code, UUID, text utilities, dates, colors, calculators, cron builder, cURL helpers and more.
The tools are built for development, testing, QA, demos and automation workflows without requiring sign-up or installation.
Pages are organized by country and category with direct, crawlable links to each tool.
🛠 Generators
17NI / UTR
Generate synthetic local-format documents for software tests and form flows.
HOTUK Person
Create complete fictional profiles for QA, demos, seed data and development.
HOTUK Company
Create fictional company data for tests, screens and integrations.
Sort Code / Account
Generate synthetic banking data for screens, tests and documentation.
Postcode / Address
Generate local-format addresses for forms, shipping flows and prototypes.
UK Names
Generate fictional names for lists, prototypes, demos and test datasets.
Credit Card
Test number
HOTUUID / ULID
Generate UUIDs and ULIDs for tests, databases, logs and integrations.
Secure Password
Create strong passwords with configurable length, symbols and options.
HOTNicks / Nicknames
Generate fictional names for lists, prototypes, demos and test datasets.
Special Letters
Stylized text
Symbols to Copy
Special characters
Lorem Ipsum AI
Text via AI
Placeholder Image
Generate image URL
QR Code
Generate QR Codes for links, text, contacts and interface testing.
Random Numbers
Defined range
Randomizer
Draw from list
✓ Validators
3T Text
15Char Counter
Count characters, words, lines and paragraphs for SEO, UI limits and documentation.
Uppercase/Lowercase
Transform, review and normalize text for systems, SEO and documentation.
Slug / Case Converter
Generate clean slugs for URLs, headings, technical SEO and routes.
Reverse Text
Transform, review and normalize text for systems, SEO and documentation.
Sort Alphabetically
Transform, review and normalize text for systems, SEO and documentation.
Remove Accents
Remove accents from text for search, slugs, integrations and normalisation.
Number to Words
Convert numbers and values into words for documents and tests.
Word Occurrence
Transform, review and normalize text for systems, SEO and documentation.
Text to HTML
Convert plain text into safe HTML snippets for previews, emails and documentation.
Trim Text
Transform, review and normalize text for systems, SEO and documentation.
Split String
Transform, review and normalize text for systems, SEO and documentation.
Char Info
Transform, review and normalize text for systems, SEO and documentation.
Custom Letters
Create Unicode text styles for headings, social posts, prototypes and visual tests.
Remove/Replace \n
Transform, review and normalize text for systems, SEO and documentation.
Spelling Corrector
Review spelling, accents and punctuation in test copy.
% Calculators
7Percentage
Calculate percentages, increases, discounts and percentage change.
GCD / LCM
Calculate percentages, proportions, dates and values for tests and docs.
Prime Factorization
Calculate percentages, proportions, dates and values for tests and docs.
Rule of Three
Calculate percentages, proportions, dates and values for tests and docs.
Division Remainder
Calculate percentages, proportions, dates and values for tests and docs.
Geometric Areas
Calculate areas for circles, rectangles, triangles, trapeziums and other shapes.
Roman Numerals
Calculate percentages, proportions, dates and values for tests and docs.
📅 Dates
3{} Code
19JSON Formatter
Format, validate and compare JSON for APIs, fixtures and technical docs.
JWT Decoder
Decode and inspect header and payload from test or redacted JWTs.
Base64
Encode and decode text as Base64 for APIs, logs and technical examples.
Hash Generator
Generate MD5, SHA-1, SHA-256 and SHA-512 hashes for test text.
URL Encoder
Encode and decode URLs, parameters and query strings.
CSV ↔ JSON
Format, validate and compare JSON for APIs, fixtures and technical docs.
Text Diff
Use code utilities for APIs, tokens, hashes, SQL and automation workflows.
RegEx Tester
Use code utilities for APIs, tokens, hashes, SQL and automation workflows.
SQL Formatter
Use code utilities for APIs, tokens, hashes, SQL and automation workflows.
Markdown Preview
Preview Markdown for READMEs, documentation and technical notes.
JSON → TypeScript
Convert JSON into TypeScript interfaces for APIs, mocks and contracts.
Meta Tag Preview
Check title, description and URL in SEO and social sharing previews.
YAML ↔ JSON
Format, validate and compare JSON for APIs, fixtures and technical docs.
Base Converter
Use code utilities for APIs, tokens, hashes, SQL and automation workflows.
JWT Generator
Use code utilities for APIs, tokens, hashes, SQL and automation workflows.
IP / CIDR Calculator
Use code utilities for APIs, tokens, hashes, SQL and automation workflows.
SSL Cert Decoder
Use code utilities for APIs, tokens, hashes, SQL and automation workflows.
JSON Diff
Format, validate and compare JSON for APIs, fixtures and technical docs.
JSON Schema
Format, validate and compare JSON for APIs, fixtures and technical docs.