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Base64 encoding converts binary data into a text format using 64 printable ASCII characters. It is used to embed binary data (images, files, PDFs) inside text-based formats like HTML, CSS, JSON, and email. Base64 increases file size by about 33% compared to the original binary. Common use cases include embedding small images directly into HTML as data URLs, sending binary files in API requests as JSON strings, and storing binary data in databases that only support text fields.

A JWT (JSON Web Token) has three Base64URL-encoded sections separated by dots: the header, the payload, and the signature. To decode it, split on the dots and Base64-decode each section. The header contains the algorithm type. The payload contains the claims, including user ID, expiration time, and roles. The signature verifies authenticity and requires the secret key to check. You can decode the header and payload without the secret, but you cannot verify the signature without it.

WCAG (Web Content Accessibility Guidelines) color contrast requirements specify the minimum contrast ratio between text and its background. The standard AA level requires 4.5:1 contrast for normal text and 3:1 for large text. The stricter AAA level requires 7:1. Sufficient contrast ensures that people with low vision or color blindness can read content. Contrast is calculated from the relative luminance of foreground and background colors. Most jurisdictions treat WCAG AA compliance as the baseline for accessibility law.

A cron job is a scheduled task that runs automatically at specified times on Unix-based systems. Cron expressions have five fields: minute (0-59), hour (0-23), day of month (1-31), month (1-12), and day of week (0-7). For example, the expression '0 9 * * 1' runs every Monday at 9:00 AM. Asterisks mean 'every'. Commas separate multiple values. Hyphens specify ranges. Slashes specify step intervals. '*/15 * * * *' means every 15 minutes. The cron job builder above generates expressions from plain-English settings with a preview of the next five run times.

JSON requires all keys to be double-quoted strings, values to be one of six types (string, number, boolean, null, object, or array), and no trailing commas after the last item in an object or array. Common errors include single-quoted strings, unquoted keys, trailing commas, and using undefined or functions as values. Paste your JSON into the formatter above to automatically fix indentation, highlight syntax errors, and see the structure clearly. The formatter shows the exact line and character where any error occurs.

URL encoding (percent-encoding) converts characters that are not allowed in URLs into a percent sign followed by two hex digits. Spaces become %20 (or + in query strings), ampersands become %26, and equals signs become %3D. You need URL encoding when including user input in a URL, building query strings programmatically, or passing a URL as a parameter inside another URL. Failing to encode special characters is a common cause of broken links and API request failures.

Enter your pattern in the regex field, then paste sample text in the test area. The tester highlights all matches instantly. Start with a simple pattern and add complexity gradually. Use capture groups (parentheses) to extract specific parts of matches. Toggle flags: i for case-insensitive, g for global (find all matches), m for multiline. Always test against edge cases and not just your expected input. The regex tester above shows match details and capture group values for each match as you type.

Markdown is converted to HTML by a parser that transforms Markdown syntax into HTML tags. Asterisks around text become bold or italic tags. Hash signs become heading tags (h1 through h6). Hyphens at line starts become list items. Backticks become code tags. Links in [text](url) format become anchor tags. Most Markdown parsers also support GitHub Flavored Markdown extensions including tables, task lists, strikethrough, and fenced code blocks with syntax highlighting. The converter above shows a live HTML preview as you type.