Base64 is a binary-to-text encoding scheme that represents any byte sequence using 64 printable ASCII characters (A-Z, a-z, 0-9, +, /). It exists to make binary or special-character data safe to embed in contexts that only reliably support plain text, like JSON fields or email bodies.

Why does Base64 end with == or = sometimes?

Base64 groups input into 3-byte chunks and encodes each as 4 output characters. If your input length isn't a multiple of 3 bytes, the encoder pads the final group with = (one pad if 2 bytes are left over, two pads if 1 byte is left over) so the output always ends on a clean 4-character boundary.

Is Base64 encoding the same as encryption?

No, and this is the most common misconception about it. Base64 is fully and instantly reversible by anyone with no key or password — it provides zero confidentiality. Never rely on Base64 alone to protect sensitive data; use real encryption (like AES) if you need actual security.

Can I encode binary files like images with this tool?

This tool handles text strings typed or pasted directly. To Base64-encode an actual image or binary file, use the separate Image to Base64 tool on this site, which reads file bytes directly rather than requiring you to paste them as text.

Why do I get an "Invalid Base64 string" error when decoding?

This happens when the input contains characters outside the valid Base64 alphabet (anything other than A-Z, a-z, 0-9, +, /, and trailing = padding), or when the length isn't consistent with valid Base64 padding rules — often caused by accidentally including surrounding quotes, line breaks, or truncated text when copying a Base64 string.

What is the difference between standard Base64 and Base64URL?

Standard Base64 uses + and / in its alphabet, both of which have special meaning in URLs. Base64URL substitutes - for + and _ for / (and often omits padding) specifically so the encoded output can be used directly in a URL or filename without additional escaping — this is the variant used inside JWTs.

Does Base64 encoding reduce or increase file size?

It increases size by roughly 33%, since every 3 raw bytes become 4 encoded characters. This overhead is the tradeoff for gaining safe plain-text compatibility, which is why Base64 is used for embedding rather than for compression.

Can I decode a JWT with this tool?

You can decode the header and payload segments (the parts before and between the dots) since they are Base64URL-encoded JSON, but you'll need to substitute - and _ back to + and / first. The signature segment is not meant to be human-readable and cannot be verified without the signing key.

Is my text sent to a server when I encode or decode it?

No. Both operations run using the browser's native btoa()/atob() functions combined with local JavaScript string processing — nothing you type is ever transmitted anywhere, which is important if you're encoding credentials, tokens, or other sensitive values.

Why did decoding my Base64 string produce garbled or broken characters?

This almost always means the original encoding did not account for Unicode correctly — for example, if the string was encoded somewhere using plain btoa() without the UTF-8 percent-encoding step, multi-byte characters can come out corrupted. Re-encode the original text using this tool (which handles Unicode properly) to get a string that decodes back cleanly.

All ToolsEncode / Decode Base64

Encode / Decode Base64

Encode plain text to Base64 or decode Base64 back to text. Handles Unicode and special characters.

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What is Encode / Decode Base64?

Encode/Decode Base64 is a free online tool that encodes plain text to Base64 format or decodes Base64 back to readable text. Base64 is one of the most common encodings in web development, and understanding what it actually does — and doesn't do — matters for using it correctly.

Base64 is a binary-to-text encoding scheme: it takes arbitrary bytes and represents them using only 64 printable ASCII characters (A-Z, a-z, 0-9, plus + and /), which makes the result safe to embed anywhere that expects plain text — a JSON field, an XML document, an HTTP header, or a URL — without worrying about unprintable control characters or encoding mismatches corrupting the data in transit. It works by regrouping input bytes into 6-bit chunks (since 2^6 = 64) instead of the usual 8-bit bytes, then mapping each 6-bit value to one of the 64 allowed characters; because 3 bytes (24 bits) divide evenly into four 6-bit groups, Base64 output is always a multiple of 4 characters, padded with = when the input isn't a clean multiple of 3 bytes.

You'll run into Base64 constantly in real systems: a data URI like data:image/png;base64,iVBORw0KG... embeds an entire image directly inside HTML or CSS with no separate file request; the header.payload.signature structure of a JWT has its first two segments Base64URL-encoded JSON, which is why anyone can read (though not forge) a JWT's claims without a library; HTTP Basic Authentication sends credentials as Authorization: Basic <base64 of user:pass>; and email systems have used Base64 (specifically the MIME standard) since the 1990s to safely transmit binary attachments over protocols originally designed only for 7-bit ASCII text.

The single most important thing to understand about Base64 is that it is encoding, not encryption. There is no secret key involved, and no cryptographic transformation happens — any Base64 string can be decoded back to its original bytes instantly by anyone, with no password required. Seeing Base64 in a config file, a cookie, or a URL parameter should never be read as a security measure; it's purely a format-compatibility trick for making binary or special-character data safe to transport as plain text.

Everything here processes as plain UTF-8 text. This tool correctly round-trips Unicode characters — accented letters, CJK text, emoji — by percent-encoding them before the browser's native btoa() call and reversing that with decodeURIComponent after atob(), since btoa() alone only supports the Latin-1 character range and throws on anything outside it. All processing happens locally in your browser tab; nothing you type is ever transmitted to a server.

How It Works

Encoding first runs your text through encodeURIComponent to percent-escape any character outside the Latin-1 range, then unescape to convert those percent sequences into raw Latin-1 bytes, and finally passes the result to the browser's native btoa() function, which performs the actual Base64 transformation. Decoding reverses this exact chain: atob() converts the Base64 string back to a raw byte string, escape() re-encodes any byte above 127 into percent-escaped form, and decodeURIComponent reconstructs the original Unicode text from those escapes. This three-step chain — rather than calling btoa()/atob() directly — is specifically what allows the tool to handle any Unicode input correctly instead of throwing an InvalidCharacterError, which is what plain btoa() does the moment it encounters a character outside Latin-1.

How to Use

1
Paste text or binary data
Enter the text you want to encode, or paste a Base64 string you want to decode.
2
Encode or decode
Click "Encode to Base64" to convert text to Base64, or "Decode from Base64" to reverse the operation.
3
Copy the result
Copy the encoded or decoded output to your clipboard for use in code, APIs, or emails.
4
Encode files (optional)
Use the Encode Image to Base64 tool to convert image files to Base64 data URLs for embedding in HTML or CSS.

Who Uses This Tool

🔑

HTTP Basic Authentication

Encode "username:password" to Base64 for use in the Authorization: Basic header of HTTP requests.

🖼️

Data URI Inspection

Decode a data:image/png;base64,... URI to inspect or extract the raw bytes of an embedded image.

📧

Email Attachment Encoding

Encode binary attachment content to Base64 to embed it safely within MIME-formatted email messages.

🔐

JWT Payload Reading

Decode the Base64URL-encoded middle section of a JWT token to read its JSON payload without a library.

📦

API Payload Encoding

Encode binary or Unicode content to Base64 so it can be transmitted safely through JSON API fields.

🛠️

Debugging Encoded Strings

Quickly decode an unknown Base64 string encountered in logs, configs, or source code to see its raw value.

Why Choose This Tool

Unicode Support

Handles multi-byte Unicode characters correctly using percent-encoding before the btoa call, preventing encoding failures.

Clear Error Messages

Invalid Base64 input produces a descriptive error rather than silently returning garbage, so issues are immediately obvious.

One-Click Mode Switch

Toggle between encode and decode modes with a single button tap without clearing your existing text.

Instant Processing

Encoding and decoding run synchronously in the browser so results appear the moment you click.

No Size Limit

Handles arbitrarily long strings in the browser without any file-size restrictions or timeouts.

Private by Default

No text is ever sent to a server, making this safe for encoding credentials, tokens, and sensitive payloads.

Also Try

URL Encode/Decode Image to Base64 Hash Generator JWT Generator JSON Formatter Regex Tester

Key Benefits

Encode or decode with a single click
Correctly handles Unicode text — accented letters, CJK, emoji
Shows clear, specific error messages for invalid or malformed Base64 input
Standard alphabet output (A-Z, a-z, 0-9, +, /) with correct = padding
Copy output instantly with one click
No data leaves your browser — safe for credentials and tokens

Frequently Asked Questions

Also Known As

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