OneTaskValidators and Testers
JSON, YAML, CSS, Email, Regex and XPath Checks Online
Tools that check your work. Validate JSON, YAML, CSS and email addresses, test regular expressions, JSONPath and XPath queries, and inspect Unicode text. Each one points to the exact line or character that's wrong rather than just saying no.
42 tools tagged Validators
.env File Checker
Lint a .env file for syntax errors, duplicates and weak secrets.
APCA Contrast Checker
APCA Lc contrast score with WCAG 3 draft levels and minimum text sizes.
Audio Info Inspector
Read the sample rate, channels, bitrate and levels of any audio file.
Checksum Verifier
Check several files against a SHA256SUMS list, like sha256sum -c.
Contrast Checker
Check colour contrast against WCAG and APCA.
CORS Tester
Test a URL for CORS headers or analyse pasted ones.
CSP Tester
Explain a CSP, flag weaknesses, and test whether a URL would load.
CSS Selector Tester
Test a CSS selector against pasted HTML and list every matching element.
CSS Validator
Find typos, missing semicolons and unknown properties in pasted CSS.
CVE ID Validator
Check a list of CVE IDs for format errors and duplicates.
CVSS Calculator
Score a vulnerability with CVSS 3.1 from metrics or a vector.
Data Breach Notification Deadline Calculator
Work out the exact deadlines to report a data breach.
DC Offset Checker
Measure the DC offset of each channel and remove it.
Email Validator
Check a list of email addresses for syntax errors and likely typos.
File Hash Checker
Hash a file and check it against the published checksum.
Heading Structure Checker
List a page's h1–h6 in order and flag skipped levels, missing h1, empties.
Hidden Character Inspector
Find the invisible characters breaking your text, then strip them.
Homograph Checker
Detect lookalike domains that swap letters to imitate real brands.
HSTS Preload Checker
Check a Strict-Transport-Security header against the HSTS preload rules.
HTML Validator
Find unclosed tags, duplicate ids and bad nesting in pasted HTML.
Image Dimensions Inspector
Pixel size, aspect ratio, megapixels and CSS size for any image.
JSONPath Tester
Run JSONPath queries against pasted JSON and see every match.
Keyboard Navigation Tester
Audit HTML for controls that keyboard users cannot reach, operate or see.
Meta Tag & Open Graph Checker
Check title, description, canonical, Open Graph and Twitter card tags in pasted HTML.
Password Hash Identifier
Identify bcrypt, Argon2, sha512crypt, NTLM, MD5 and other hash formats.
Password Policy Tester
Test a list of passwords against length, character and banned-word rules.
Phase Checker
Check a stereo file for phase problems and mono compatibility.
Posture Checker
Webcam posture checker with slouch warning and live pose tracking. Nothing uploaded.
Pwned Password Checker
Check a password against breach data without sending the password.
Regex Tester
Test a regex and see every match and capture group.
Schema Markup Validator
Validate JSON-LD schema.org markup for required properties and format errors.
Sitemap Validator
Validate sitemap.xml and sitemap index files against the sitemaps.org protocol.
SSL Certificate Inspector
Decode a PEM certificate and check its dates, names and fingerprints.
SVG Validator
Find unclosed tags, bad path data and broken references in SVG.
Tab Order Tester
List every Tab stop in your HTML in order and flag focus order problems.
Title Length Checker
Check page titles and meta descriptions by pixel width, not just characters.
Touch Target Checker
Check a control's size and spacing against WCAG, Apple and Android minimums.
URL Validator
Check a list of URLs for syntax errors, one per line.
UUID Validator
Check a list of UUIDs and decode their version, variant and timestamp.
Viewport Inspector
Live viewport size, pixel ratio and active breakpoint.
WCAG Checker
Find WCAG accessibility failures in pasted HTML, with the criterion each breaks.
XPath Tester
Test XPath expressions against pasted XML or HTML instantly.