Free Base64 Encoder/Decoder

Base64 is a binary-to-text encoding scheme that converts any data, text, images, files, into a string of 64 printable ASCII characters (A-Z, a-z, 0-9, +, /). It was originally designed for email attachments where only ASCII could be transmitted safely, but is now used everywhere: data URIs, JWT tokens, API payloads, and storing binary data in JSON. Despite the name, Base64 is NOT encryption, anyone can decode it, and it provides zero security.

Base64 takes 3 bytes (24 bits) of input and splits them into 4 chunks of 6 bits each. Each 6-bit chunk (0-63) maps to one of 64 printable characters. The result is always ~33% longer than the input. If the input length is not divisible by 3, one or two "=" padding characters are added to the end to make the output length a multiple of 4.

Common uses include: (1) Embedding small images directly in HTML/CSS as data URIs, avoiding extra HTTP requests. (2) Sending binary data through text-only protocols like email or JSON APIs. (3) Encoding JWT payloads (Base64URL variant). (4) Storing binary blobs in databases that only accept strings. (5) Basic HTTP authentication (username:password in the Authorization header). (6) Obfuscating data from casual inspection, but never as security.

Standard Base64 uses + and / characters, which have special meanings in URLs (+ means space, / separates path segments). URL-safe Base64 (Base64URL, per RFC 4648) replaces + with - (hyphen) and / with _ (underscore), making the output safe to use in URLs, query parameters, or filenames without any additional escaping. URL-safe Base64 often also omits the = padding. Use URL-safe when your Base64 will appear in a URL or filename; use standard otherwise.

No, Base64 is NOT encryption. It is a reversible encoding, anyone with the Base64 string can decode it back to the original data using any Base64 decoder (including this one). Do not use Base64 to "hide" passwords, API keys, or sensitive data. If you need security, use real encryption like AES, or hashing like SHA-256. Base64 is purely for format conversion, not confidentiality.

Base64 encoding increases data size by approximately 33% (the output is 4/3 the input length, plus padding). For every 3 bytes of input, you get 4 bytes of Base64 output. A 1 KB file becomes roughly 1.37 KB of Base64. If you gzip before Base64, you can offset some of the size increase for highly compressible data. Avoid Base64-encoding large files that will be transmitted over bandwidth-limited connections.

Yes, Base64 was designed for exactly this purpose. You can encode any binary file (images, PDFs, audio) into a Base64 string to embed in JSON, HTML data URIs, or text-only APIs. However, the 33% size overhead makes Base64 inefficient for large files, streaming binary or using multipart/form-data is usually better. This tool is designed for text input; to encode binary files, use a browser tool that supports FileReader or a CLI utility like base64.

Yes. This tool handles full Unicode including emoji, CJK characters, and combining marks. Internally, the input text is first encoded to UTF-8 bytes, then those bytes are Base64-encoded. This is the safest way to Base64 any text because it avoids the mojibake issues that plague naive Base64 implementations when handling non-ASCII input. For example, the emoji "😀" becomes "8J+YgA==" in Base64.

The = characters are padding. Base64 encodes in groups of 3 input bytes → 4 output characters. If the input length is not divisible by 3, the output is padded with = to reach a multiple of 4. One = means the last input group had 2 bytes; two == means 1 byte. Some implementations (especially Base64URL in JWT) omit padding entirely. When decoding, most decoders (including this tool) accept both padded and unpadded input.

Not without percent-encoding. Standard Base64 contains + and / which have special meanings in URLs, and = which can cause parsing issues. For URLs, always use URL-safe Base64 (Base64URL) which replaces + with -, / with _, and often drops the = padding. Alternatively, percent-encode the standard Base64 string. This tool outputs both variants so you can pick the right one for your context.

JavaScript (browser): atob(str) decodes, btoa(str) encodes, ASCII only, use TextDecoder/TextEncoder for Unicode. Node.js: Buffer.from(str, "base64").toString() decodes, Buffer.from(str).toString("base64") encodes. Python: base64.b64decode(str) / base64.b64encode(bytes). For URL-safe: base64.urlsafe_b64decode. Shell: echo "text" | base64 / echo "SGVsbG8=" | base64 -d. This tool does all of these correctly including Unicode.

No. All Base64 encoding and decoding happens 100% in your browser using native JavaScript APIs (TextEncoder, btoa, atob). Your input never leaves your device, and nothing is logged or stored on our servers. The optional history feature uses localStorage, which stays on your browser only. This makes the tool safe for sensitive data, internal API payloads, and anything you would not want to send to a third party.