Formats & configs
Validate JSON, YAML, XML, and CSV locally so payloads and configs are clean and private.
Fast, private, free
Validate sensitive data without uploading a thing.
Every validator runs in your browser, so nothing leaves your device. Check JSON, passwords, cards, links, and metadata with clear rules, examples, and FAQs that show what is being checked and why.
- ✔ Data never stored or sent
- ✔ No accounts or downloads
- ✔ New validators added weekly
What can you check?
Sanity-check JSON or YAML before committing changes.
Score password strength locally, and keep secrets off the network.
Validate URLs, meta lengths, and titles before you publish.
Run Luhn checks on cards or IDs without exposing numbers.
Used by developers, security engineers, and content teams worldwide.
Security & data sanity
Score passwords, run Luhn checks, and verify IDs without sending secrets or PII to any server.
Web & content checks
Inspect URLs, meta lengths, and word counts before publishing or sending to clients, with no screenshots or uploads required.
Browse by topic
Pick a validator category
Formats, security, developer utilities, text, data, and web. Each category links to validators teams use to catch issues before release.
Format Validators•3 tools
Debug failing deploys
Validate JSON, YAML, XML, CSV, and HTML with instant syntax checks and prettified output for quick fixes.
Example validators
Developer Validators•2 tools
Test a regex before merging
Everyday developer helpers like regex tests, UUID checks, and IP/port validation for quick sanity checks.
Example validators
Security Validators•1 tool
Raise password quality
Password strength, entropy, and token format checks that never leave your browser.
Example validators
Text Validators•1 tool
Hit content targets
Counters and readability tools for writers, marketers, and support teams.
Example validators
Data Validators•1 tool
Validate customer input early
Validate IBANs, credit cards, ISBNs, VINs, and barcodes with checksum and pattern checks.
Example validators
Web Validators•3 tools
Publish with confidence
URL, sitemap, robots, and metadata checks for marketers and SEO teams.
Start here
High-demand validators
These are the browser-local tools currently published for direct discovery: web metadata and structured-data checks, HTML, Markdown and property-list checks, port and regex tools, hashing, word counts, and IMEI validation. Each is linked directly from the homepage so crawlers and users can reach the published validators in one step.
web
Web App Manifest SEO Validator & PWA Install QA
Validate manifest.json locally for PWA installability, mobile install metadata, app names, start_url, display mode, theme colors, and icon entries before launch.
Open validator →format
Plist Validator
Validate Apple plist files (XML or binary/base64) locally with clear errors.
Open validator →web
JSON-LD SEO Validator & Rich Result Schema Checker
Validate rendered JSON-LD structured data for schema.org syntax, rich-result readiness, visible-content alignment, and crawlable schema blocks before publishing.
Open validator →data
IMEI Validator
Validate IMEI numbers with Luhn checksum client-side.
Open validator →developer
Port Validator
Check port numbers for valid ranges before using them in configs.
Open validator →format
Markdown Validator
Lint Markdown locally with remark-lint, surface rule IDs/line numbers, and keep content private.
Open validator →format
HTML Validator (light)
Check HTML structure with HTMLHint rules—mismatched tags, casing, and basic issues—all client-side.
Open validator →Featured picks
Most-requested validators this week
Start with these popular tools, or open a category hub to browse every validator we’ve launched.
web
JSON-LD SEO Validator & Rich Result Schema Checker
Validate rendered JSON-LD structured data for schema.org syntax, rich-result readiness, visible-content alignment, and crawlable schema blocks before publishing.
Open validator →data
IMEI Validator
Validate IMEI numbers with Luhn checksum client-side.
Open validator →format
Plist Validator
Validate Apple plist files (XML or binary/base64) locally with clear errors.
Open validator →web
Web App Manifest SEO Validator & PWA Install QA
Validate manifest.json locally for PWA installability, mobile install metadata, app names, start_url, display mode, theme colors, and icon entries before launch.
Open validator →Recently added
Hot off the roadmap
We publish new validators every wave. Here are the latest across formats, security, and web.
Why people bookmark us
Validation that protects privacy and saves time.
Private by design
Runs fully in the browser with no storage or logging, so payloads, tokens, and drafts stay local.
Transparent rules
Every tool shows the rules, examples, FAQs, and disclaimers so you know how results are made.
Always current
New validators ship every wave. Request one from the contact page and we’ll prioritize it.