Free Online Base64 Decoder -- Seven Base64 Tools in One Place
This page provides seven browser-based Base64 utilities accessible from the left sidebar. Every tool runs entirely in your browser -- no data is uploaded, no account is required, and nothing is stored. Select a tool from the sidebar, paste or upload your content, and results appear immediately.
Base64 Decoder
Converts a standard Base64 string back to plain text. Handles UTF-8 characters, optional padding, and shows the exact error if the input is malformed.
Base64 Encoder
Encodes plain text to standard Base64 (RFC 4648) with correct UTF-8 handling. Output is padded and ready for use in HTML data URIs, JSON fields, and HTTP headers.
URL-Safe Decode
Decodes Base64url strings that use - and _ instead of + and /. Adds padding automatically before decoding, making it ideal for JWT payload inspection.
URL-Safe Encode
Encodes text to Base64url without padding. Output is safe for URL query strings, path segments, file names, and JWT token segments.
Base64 to Image
Renders a Base64 data URL or raw Base64 image string as a live image preview. Supports PNG, JPEG, GIF, WebP, and SVG.
Image to Base64
Reads an image file from your device and outputs the raw Base64 string. File is never uploaded -- conversion uses the browser FileReader API locally.
Online Base64 Decoder -- Convert Base64 Strings Back to Plain Text
Base64 encoding is used throughout modern software: in email attachments, API tokens, data URIs, and configuration files. The free Base64 decoder on this page reverses that encoding instantly. Paste any Base64 string and the original text is recovered in the output panel without any server call.
How the Base64 Decoder Works
The decoder uses the browser's native atob() function combined with decodeURIComponent and escape to correctly handle the full UTF-8 character range, including accented characters and emoji. If the input is not valid Base64 -- due to an invalid character, incorrect padding, or wrong length -- the decoder shows a clear error message rather than silently returning garbled output.
Common Uses for Base64 Decoding
Base64 strings appear in many everyday development tasks: inspecting the payload of a JWT token, reading email attachment content, examining HTML data URIs embedded in CSS, reviewing API responses that contain binary data as strings, and debugging OAuth authorization headers. Having a fast, free, online Base64 decoder available without signup saves time during these workflows.
Free Base64 Encoder -- Encode Text to Base64 Online
The Base64 encoder converts any plain text to a standard Base64-encoded string. The output is padded with = characters where required and uses the full standard alphabet (A-Z, a-z, 0-9, +, /) defined by RFC 4648 Section 4. It is ready to paste directly into HTML src attributes, JSON string values, Basic Auth headers, or MIME email parts.
UTF-8 and Special Character Support
Many online Base64 encoders break when the input contains non-ASCII characters such as accented letters, Chinese characters, or emoji. This encoder first converts the input through encodeURIComponent to produce a UTF-8 byte sequence before encoding to Base64, so the full Unicode character set is handled correctly without corruption.
Base64 Is Not Encryption
Base64 is purely an encoding format that makes binary data safe to transmit as ASCII text. It does not provide any confidentiality. Anyone who receives a Base64-encoded string can decode it instantly using any Base64 decoder. Do not use Base64 to protect passwords, API keys, or other sensitive information.
Free URL-Safe Base64 Decode and Encode Online
URL-safe Base64 (also called Base64url) is a variant defined in RFC 4648 Section 5 that replaces the + and / characters with - and _ respectively, and typically omits the = padding. This makes the encoded string safe to include directly in URLs, file names, and HTTP headers without percent-encoding.
Decoding JWT Tokens
A JSON Web Token consists of three URL-safe Base64-encoded segments separated by dots: the header, the payload, and the signature. To inspect the claims in a JWT, take the middle segment (the payload), paste it into the URL-Safe Decode tool, and the decoded JSON is shown immediately. This is useful for debugging authentication issues, verifying expiry times, and checking which permissions a token grants.
OAuth and PKCE Code Verifiers
The OAuth 2.0 PKCE extension uses URL-safe Base64 to encode the code verifier and code challenge. The URL-Safe Encode tool on this page produces unpadded Base64url output that matches the format required by the OAuth specification, making it useful for generating test values and debugging authorization flows.
Base64 to Image -- Preview Base64 Image Data URLs Online Free
Developers frequently encounter Base64-encoded images embedded in HTML, CSS, JSON responses, or database records. Visually inspecting these strings requires rendering them as images, which typically means writing a small script or using an external tool. The free Base64 to Image tool on this page renders the image directly in the browser with no server involvement.
What Is a Base64 Data URL
A data URL is a URI scheme that embeds file content inline using Base64 encoding. The format is data:[mediatype];base64,[base64data]. For images, a complete data URL might look like data:image/png;base64,iVBORw0K.... Browsers treat data URLs as equivalent to external image URLs, loading the content from memory rather than making an HTTP request.
Image to Base64 Conversion
The Image to Base64 tool reads an image file from your local device using the browser's FileReader API and outputs the raw Base64 string. The file is never transmitted to a server. The output includes the file name, MIME type, file size, and Base64 character count so you can assess whether the encoded string is suitable for inline use. Very large images produce very long Base64 strings that may affect page load performance if embedded in HTML.
Free Base64 Validator -- Check Base64 Strings Online
The Base64 Validator checks whether a string is correctly formed Base64 before you attempt to decode or use it. It detects whether the string uses the standard alphabet or the URL-safe alphabet, reports the input character count, the decoded byte length, and shows a short preview of the decoded content so you can confirm the data is what you expect.
What Makes a Base64 String Invalid
The most common reasons a Base64 string fails validation are: characters outside the allowed alphabet (such as spaces, angle brackets, or percent-encoded sequences), incorrect padding where the string length modulo 4 does not produce a valid byte count, and mixed alphabets where both + and - appear in the same string. The validator identifies and reports each of these problems clearly.
Related Encoding and Developer Tools
If you work with encoded data and developer utilities regularly, these other free tools on the site complement this Base64 toolkit:
- JSON Formatter -- format, validate, minify, and convert JSON in the browser
- HTML Viewer -- live HTML preview, minifier, and tag stripper
- Code Formatter -- format HTML, CSS, JSON, XML, and JavaScript in one tool
- AI Table Generator -- generate formatted HTML tables with AI