HTML lang Validator - Online Check Language Tag
Validate a language tag like en‑US or zh‑Hans against the IANA registry. Ensure correct HTML lang attribute.
UD5 Toolkit
Validate your Web App Manifest for installability, completeness, and best practices
<link rel="manifest" href="/manifest.json"> and is essential for making your web app installable.
<link> tag in the <head> section of every HTML page: <link rel="manifest" href="/manifest.json">application/manifest+json. For full PWA support, you'll also need a service worker registered on your pages.
"/" or "/app/"). If not specified, the browser defaults to the directory containing the manifest.
display not set to standalone/fullscreen/minimal-ui, or the user has previously dismissed the prompt. Use this validator to check your manifest and also verify your service worker registration and HTTPS setup.
short_name is not provided, the browser truncates name for the home screen label, which may result in an awkward display. Providing both gives you full control over how your app name appears in different contexts.
Validate a language tag like en‑US or zh‑Hans against the IANA registry. Ensure correct HTML lang attribute.
Paste an HTML snippet and check for common ARIA mistakes: missing labels, invalid roles, and aria‑hidden misuse. Educate your team.
Paste any DNS record and check if its format is valid for the selected record type (A, AAAA, CNAME, MX, TXT, SRV). Prevents typos.
Paste a WebVTT file and instantly check for syntax errors. Validate timestamps and cue formatting. Essential for video devs.
Paste an SVG and check if the graphic‑aria roles are used correctly. Improve accessible diagrams and icons.
Paste JavaScript and catch syntax errors instantly with line numbers. Lightweight pre‑commit check. Local.
See how a PWA can extend content into the title bar area on desktop. Customize the window controls overlay.
Enter a text color and background color and instantly see if the combination passes WCAG AA and AAA ratio. Safe colors.
Paste HTML snippet and highlight interactive elements missing accessible labels. Quick a11y audit.
Create a fully accessible form by adding fields; the tool generates the proper labels, inputs, and ARIA attributes. Copy the clean HTML.
Paste a set of hex colors and simulate how they appear with common color vision deficiencies. Get contrast warnings.
Flip a coin with adjustable bias (e.g., 70% heads). Used for random decision-making when you want to gently influence outcomes. History & stats shown.
Calculate the perceived brightness of an RGB color and determine if black or white text is more readable. Accessibility tool.
Convert .srt subtitles to .vtt format for web video players. Preserves all timestamps and formatting. Local.
Convert plain text into HTML‑safe strings by escaping <, >, &, and quotes. Insert into code safely. Local copy.
Build a 3D card flip effect and toggle backface‑visibility. See the hidden back face. Copy the complete CSS.
Create a 5‑star rating widget using only HTML and CSS. Customize colors and size. Copy the clean code.
Search common dream symbols and their traditional meanings. For entertainment and self-reflection. Static data.
Encode latitude/longitude into a geohash string and decode a geohash back to coordinates with precision info. Local algorithm.
Enter latitude and longitude and get a human‑readable address using the browser's built‑in reverse geocoding (if available).
Pick a base color and generate a 10‑step scale where each step meets a specific contrast ratio against white or black. Export as CSS custom properties.
Paste a string of weather emojis and get a written weather forecast. Fun and educational emoji tool.
Reverse any short video clip and download the backward version. Fun for creative effects. Browser‑based.
View the moon phase for any date in past or future. See full moon dates and eclipses for a given year.
Automatically restore natural colors to a photo by removing color casts. Gray world algorithm. One‑click fix. Canvas.
Shift the color temperature of your photo towards warm (orange) or cool (blue). Instant canvas filter. Download result.
Enter any number up to trillion and get the English word representation. For filling out checks or legal documents.
Instantly convert plain text into HTML‑safe escaped characters for secure display in web pages. Prevent cross‑site scripting. All processing local.
Convert plain text lines into HTML ordered or unordered lists. Instantly copy the generated HTML to paste into your website. No hassle, fully browser-based.
Build a simple decision tree by adding yes/no nodes. Flowchart style. Export as text outline.