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UtilityBox – Free Online Utility Tools

Smart tools for daily tasks — no sign-up needed

Encoder / Decoder

Encode and decode Base64 and URL values.

Base64 Encoder Decoder Online Free — URL & HTML Encode / Decode

UtilityBox's Base64 encoder decoder online is a free, browser-local tool that covers three essential encoding formats in one place. Instantly encode or decode Base64 strings, apply URL percent-encoding to query parameters and paths, and convert special characters to HTML entities — or reverse all three operations with a single click. There is no sign-up, no file upload to a server, and no browser extension required. All processing uses native JavaScript APIs (btoa/atob, encodeURIComponent, and HTML entity maps) directly inside your browser, so your data never leaves your device. Whether you need a base64 converter for embedding images in CSS, a percent encoding tool for API requests, an html entity encoder to sanitize user content, or a jwt decoder online to inspect token payloads, this tool handles every case quickly and accurately on any modern browser — desktop or mobile.

How to Use the Base64 Encoder Decoder

  1. Open the tool and choose your encoding mode using the tabs: Base64, URL Encoding, or HTML Entities.
  2. Paste or type the text you want to convert into the input area. For Base64 decode, paste the encoded string; for URL decode, paste the percent-encoded value.
  3. Click Encode to convert your input to the encoded format, or click Decode to reverse an already-encoded string back to its original form.
  4. Review the result that appears instantly in the output field below the input area.
  5. Click the Copy button to copy the result to your clipboard, then paste it directly into your code, API request, or document.

Key Features

  • Base64 encode and decode — full round-trip support using the standard Base64 alphabet and Base64url variant for JWT compatibility.
  • URL percent-encoding — encodes and decodes all reserved and unsafe characters per RFC 3986, ideal for query strings and path segments.
  • HTML entity encoder — converts <, >, &, ", and extended characters to named or numeric HTML entities and back.
  • UTF-8 and Unicode support — correctly handles multi-byte characters, emoji, CJK scripts, and accented letters in all modes.
  • 100% browser-local processing — no server round-trips; your data stays private on your device at all times.
  • Completely free — no account, no subscription, no rate limit; use as often as you need.
  • One-click copy — copy the encoded or decoded output to the clipboard instantly without selecting text manually.
  • Works on any browser — Chrome, Firefox, Safari, and Edge on desktop and mobile, with no extensions or plugins needed.

Common Use Cases

  • Embedding images and fonts in code: Convert image files or font binaries to Base64 strings and embed them directly in HTML as data URIs (e.g., src="data:image/png;base64,...") or in CSS as background-image values. This eliminates extra HTTP requests for small assets, improving page load performance and keeping self-contained HTML documents fully portable without relying on external file paths.
  • Decoding JWT payloads for API debugging: JSON Web Tokens consist of three Base64url-encoded segments. Use the base64 encode decode free tool as a lightweight jwt decoder online — paste the payload segment (the middle part after the first dot) to reveal the JSON claims such as user ID, roles, expiry timestamp, and custom attributes. This is invaluable when debugging authentication issues without needing a dedicated jwt decoder online service.
  • Building and debugging URL query strings: When constructing API requests programmatically, query-string values that contain spaces, ampersands, equals signs, or non-ASCII characters must be percent-encoded before appending to a URL. The url encoder decoder online tab lets you encode individual parameter values using the correct percent encoding tool rules and decode encoded URLs received from server logs or third-party redirects to read them in plain text.
  • Sanitizing HTML output to prevent XSS: When displaying user-generated content in a web page, characters like < and > must be converted to their HTML entity equivalents to prevent browsers from interpreting them as tags. The html entity encoder mode converts raw text to safe entity-encoded HTML in one click, making it easy to verify that your server-side sanitization logic produces the correct output before deploying code to production.

Frequently Asked Questions

What is a Base64 encoder decoder online?

A Base64 encoder decoder online is a browser-based tool that converts plain text or binary data into Base64-encoded ASCII strings (encode) and reverses that process (decode). Base64 uses a 64-character alphabet — A–Z, a–z, 0–9, +, and / — making binary data safe to transmit through text-only channels like email, JSON APIs, or HTML data URIs. UtilityBox's tool runs entirely in your browser, so nothing is sent to any server.

How does URL encoder decoder online work?

A URL encoder decoder online converts characters not permitted in a URL into their percent-encoded equivalents (e.g., a space becomes %20, & becomes %26). This percent encoding tool uses the browser's built-in encodeURIComponent and decodeURIComponent APIs. The reverse operation (decoding) turns percent-encoded sequences back into readable characters. This is essential for safely embedding query-string parameters that contain special characters.

Is the Base64 encode decode free tool safe to use?

Yes. The Base64 encode decode free tool on UtilityBox processes all data locally inside your browser using native JavaScript APIs (btoa and atob for Base64; encodeURIComponent for URL encoding). No data is transmitted to any server, stored in a database, or logged anywhere. You can safely encode sensitive strings such as API keys or token payloads knowing they never leave your device.

Can I use this as a JWT decoder online?

Yes. A JSON Web Token (JWT) consists of three Base64url-encoded segments separated by dots: header, payload, and signature. To use this tool as a JWT decoder online, copy the middle segment (the payload) and paste it into the Base64 decode tab. The tool will output the raw JSON object containing the token's claims such as sub, exp, iat, and custom fields. Note that Base64url replaces + with - and / with _, which the tool handles automatically.

What is an HTML entity encoder?

An HTML entity encoder converts special characters like <, >, &, and " into their HTML entity equivalents (&lt;, &gt;, &amp;, &quot;). This prevents browsers from interpreting those characters as HTML markup, which is critical for safely displaying user-generated content and preventing cross-site scripting (XSS) attacks. UtilityBox's HTML entity encoder handles the full range of standard named and numeric entities.

What is the difference between Base64 and percent encoding?

Base64 and percent encoding serve different purposes. Base64 converts arbitrary binary data into a 64-character ASCII string, increasing size by about 33%, and is used in email attachments, data URIs, and API payloads. Percent encoding replaces individual unsafe URL characters with a % prefix and two hex digits, preserving overall string structure. Use a base64 converter when embedding binary in text; use a percent encoding tool when constructing safe URL query strings.

Does the Base64 converter support UTF-8 and Unicode text?

Yes. The Base64 converter on UtilityBox correctly handles multi-byte UTF-8 characters, including accented letters, CJK characters, and emoji. It converts the input string to a UTF-8 byte array before applying Base64 encoding, ensuring round-trip accuracy. Similarly, the decoder reconstructs the original UTF-8 string from the byte array, so non-ASCII characters survive the encode/decode cycle without corruption.

Do I need to sign up or install anything to use this tool?

No sign-up, no installation, and no browser extensions are needed. The Base64 encoder decoder online on UtilityBox is completely free and works on any modern browser — Chrome, Firefox, Safari, and Edge on desktop and mobile. All three encoding modes (Base64, URL percent-encoding, and HTML entities) are available instantly on page load with no account required.