[ FAST · CLIENT-SIDE · DEVELOPER-FIRST ]

Free Developer Tools —
JSON, Security & AI SEO Prompts

75+ free browser-based tools for JSON formatting, security, code utilities, content processing, and AI SEO prompts.
Format JSON, decode JWTs, generate passwords, test regex, write SEO prompts, and more. Fast, private, no signup required.

Explore all tools Try JSON Formatter
75 Developer tools
5K+ Monthly users
1M+ Tool operations
99.9% Uptime SLA

What is TOOlover?

What can I do here?

Use free browser tools for JSON formatting, validation, conversion, JWT decoding, password generation, regex testing, content counting, and AI SEO prompt creation.

Do I need an account?

No. Public tools are built for immediate use without signup, API keys, or a paid plan.

Where is my data processed?

Tools run in your browser wherever possible, so pasted JSON, secrets, and text stay on your device instead of being uploaded for processing.

Why trust these tools?

Part of TOOlover

One of 67+ free developer tools in the TOOlover ecosystem. Built by developers, for developers.

Privacy First

No signup, no tracking, no data uploads. All processing happens in your browser using client-side JavaScript.

Open Source

Transparent codebase. Inspect, audit, and contribute on GitHub. No black-box algorithms or hidden fees.

JSON Formatter
Pretty-print and format JSON with configurable indentation
JSON Validator
Validate JSON syntax and structure with detailed error messages
Webhook Sender
Free online webhook sender tool to test HTTP endpoints. Send POST, GET, PUT, PATCH, and DELETE requests with custom JSON payloads, headers, and timeout options.
Payload Generator
Generate realistic webhook payloads for Stripe, GitHub, and Shopify
Webhook Receiver
Create temporary URLs to capture and inspect incoming webhooks
JWT Decoder
Decode and inspect JWT tokens — header, payload, claims, and expiry status
Secret Key Generator
Generate secure random secrets for SESSION_SECRET, JWT_SECRET, AUTH_SECRET, HMAC, API tokens, and webhooks
Password Generator
Generate cryptographically secure passwords with entropy calculation
Markdown Viewer
Convert markdown to HTML with real-time preview
Words Counter
Count words, characters, sentences, and analyze text statistics
Text Diff
Compare two texts and highlight differences line by line
HTML Preview
Preview HTML in real-time with a sandboxed iframe renderer
Case Converter
Convert text between camelCase, snake_case, kebab-case, UPPERCASE, lowercase, and more
Find & Replace
Find and replace text with regex, case-sensitive, and whole word matching
Text Sorter
Sort text lines ascending, descending, shuffle, or remove duplicates
SEO Content Brief Prompt Generator
Create a detailed AI prompt for SEO content briefs with intent, audience, outline, entities, and SERP guidance.
Blog Outline Prompt Generator
Generate a structured AI prompt for SEO-friendly blog outlines built around a keyword and audience.
Search Intent Analysis Prompt Generator
Build a prompt that asks AI to classify search intent, audience needs, SERP expectations, and content angle.
Rate Limiters
Compare token bucket, leaky bucket, fixed window, and sliding window rate limiting
Caching Simulator
Explore 5 cache strategies and 4 eviction policies with request-flow visualization

Browse by category

Explore our complete collection of developer tools organized by function. Each tool is optimized for speed and privacy — all processing happens in your browser.

JSON TOOLS

JSON Formatter
Pretty-print and format JSON with configurable indentation
JSON Validator
Validate JSON syntax and structure with detailed error messages
JSON Diff
Compare two JSON objects and highlight differences
JSON to YAML
Convert JSON to YAML format
YAML to JSON
Convert YAML to JSON format
 View all 16 json tools →

DEVELOPER TOOLS

Regex Tester
Test regex patterns with live matching and capture groups
Cron Expression Parser
Explain cron expressions in plain English and preview the next 10 run times
UUID Generator
Generate v1/v4 UUIDs, validate UUIDs, bulk generation
URL Encoder/Decoder
Encode and decode URLs and query strings
Base64 Encoder/Decoder
Encode and decode Base64 and Base64URL
 View all 17 developer tools →

SECURITY TOOLS

JWT Decoder
Decode and inspect JWT tokens — header, payload, claims, and expiry status
JWT Generator
Sign JWT tokens in the browser — HS256/384/512, RS256/384/512, PS256/384/512, ES256/384/512
Hash Generator
Generate MD5, SHA-1, SHA-256, SHA-384, and SHA-512 hashes
HMAC Generator
Generate and verify HMAC signatures for webhook verification
Secret Key Generator
Generate secure random secrets for SESSION_SECRET, JWT_SECRET, AUTH_SECRET, HMAC, API tokens, and webhooks
 View all 8 security tools →

CONTENT TOOLS

Markdown Viewer
Convert markdown to HTML with real-time preview
Words Counter
Count words, characters, sentences, and analyze text statistics
Text Diff
Compare two texts and highlight differences line by line
HTML Preview
Preview HTML in real-time with a sandboxed iframe renderer
Case Converter
Convert text between camelCase, snake_case, kebab-case, UPPERCASE, lowercase, and more
 View all 7 content tools →

UTILITY TOOLS

Time Converter
Convert between different time units
Size Converter
Convert between different file size units
Temperature Converter
Convert between Celsius, Fahrenheit, and Kelvin
Number Base Converter
Convert numbers between binary, octal, decimal, and hexadecimal
Color Converter
Convert colors between HEX, RGB, HSL, and named color formats
 View all 5 utility tools →

TECH SIMULATORS

Kafka Message Flow
Visualize how producers, partitions, and consumers move messages through a Kafka topic
Kafka Consumer Lag
Simulate consumer lag growth and recovery as produce/consume rates diverge
Kafka Consumer Rebalance
Watch partition rebalancing across a consumer group as members join and leave
Rate Limiters
Compare token bucket, leaky bucket, fixed window, and sliding window rate limiting
Caching Simulator
Explore 5 cache strategies and 4 eviction policies with request-flow visualization
 View all 12 tech simulators →

SPREADSHEET TOOLS

Excel Generator
Generate Excel files with fake sample data: choose tabs, rows, and column names with data types
Excel Splitter
Split a large Excel file into smaller files by rows or by tabs
Excel Merger
Merge multiple Excel files into one: combine into a single sheet or keep one sheet per file
 View all 3 spreadsheet tools →

AI SEO PROMPT TOOLS

SEO Content Brief Prompt Generator
Create a detailed AI prompt for SEO content briefs with intent, audience, outline, entities, and SERP guidance.
Blog Outline Prompt Generator
Generate a structured AI prompt for SEO-friendly blog outlines built around a keyword and audience.
Search Intent Analysis Prompt Generator
Build a prompt that asks AI to classify search intent, audience needs, SERP expectations, and content angle.
Keyword Cluster Prompt Generator
Create a prompt for grouping keyword lists into SEO clusters, pillar pages, supporting pages, and intent groups.
Meta Title & Description Prompt Generator
Generate a prompt for writing SEO meta titles and descriptions with variants, intent fit, and character discipline.
 View all 7 ai seo prompt tools →