Free Base64 Encoder and Decoder Online

How to use the Base64 encoder and decoder online

1. Paste any plain text into the input field and click Encode to get its Base64 representation.
2. Paste a Base64 string into the input field and click Decode to convert it back to readable text.
3. The result appears instantly and can be copied to the clipboard with one click.
4. The tool handles both standard Base64 (using + and /) and URL-safe Base64 (using - and _).
5. Nothing leaves your browser. All encoding and decoding runs locally with no server requests.

Base64 decode: reading JWT tokens, auth headers, and API responses

The base64 decoder converts any Base64 string back to its original text. The most common developer use case is inspecting JWT (JSON Web Token) payloads during debugging. A JWT has three parts separated by dots: header.payload.signature. The header and payload are both Base64 URL-encoded JSON objects. Paste just the payload section (the middle part, between the two dots) into the decoder to read the claims, expiry, and user data without needing a JWT library.

HTTP Basic Authentication headers also use Base64 encoding. The Authorization header value "Basic dXNlcm5hbWU6cGFzc3dvcmQ=" contains the Base64 encoding of "username:password". Decoding it reveals the credentials in plain text, which is why Basic Auth should only be used over HTTPS. When reviewing request logs or API documentation, this decode base64 to string tool makes it fast to inspect any encoded value without opening a code editor. For URL percent-encoding rather than Base64, the URL encoder and decoder handles that separately.

Base64 encode image and data URIs

Base64 encode image data produces a data URI that can be embedded directly in HTML or CSS without a separate file request. The format is data:[mime-type];base64,[encoded-data]. For small SVG icons and inline images this reduces HTTP requests, which matters for performance in single-file exports, email HTML templates, and CSS sprite alternatives. In an HTML img tag: <img src="data:image/png;base64,iVBO..." />. In CSS: background-image: url("data:image/svg+xml;base64,...").

The base64 decode image direction is useful when extracting an embedded image from an HTML file or CSS stylesheet. Copy the Base64 string after the comma in the data URI, decode it to verify the content, or save the decoded bytes as the original image file. Note that Base64 encoding increases data size by approximately 33 percent compared to the raw binary, so embedding large images as Base64 increases page weight significantly and is not recommended for production use beyond small icons.

JavaScript base64 encode and decode

Every modern browser and Node.js environment includes built-in Base64 support. In a browser context, btoa() encodes a string to Base64 and atob() decodes it. For example: btoa("hello world") returns "aGVsbG8gd29ybGQ=". Both functions operate on Latin-1 encoded strings. For Unicode text, convert to UTF-8 bytes first using TextEncoder before encoding.

In Node.js, the Buffer class handles Base64 encoding natively: Buffer.from("hello").toString("base64") to encode and Buffer.from(str, "base64").toString("utf8") to decode. Node.js also supports URL-safe Base64 via the base64url encoding option in newer versions. For cryptographic operations that produce Base64 output, the SHA hash generator outputs results in both HEX and Base64 format for comparison.

Python and PHP base64 encode

Python includes the base64 module in the standard library. To encode a string: import base64; base64.b64encode(b"hello") returns b"aGVsbG8=". For a plain string instead of bytes, call .encode("utf-8") first. To decode: base64.b64decode("aGVsbG8=").decode("utf-8"). For URL-safe variant: base64.urlsafe_b64encode() and base64.urlsafe_b64decode().

In PHP, the functions are base64_encode() and base64_decode(). For example: base64_encode("hello") returns "aGVsbG8=". PHP base64 encode is commonly used when generating SMTP AUTH credentials, encoding binary data for storage in a text column, and building data URIs for dynamic image generation. The second parameter of base64_decode() accepts a boolean strict mode flag that returns false if the input contains invalid characters.

Linux base64 encode and PowerShell base64 decode

On Linux and macOS, the base64 command is included with GNU coreutils. To encode a string from the terminal: echo -n "hello" | base64. The -n flag is critical: without it, echo adds a newline character that becomes part of the encoded output. To decode: echo "aGVsbG8=" | base64 --decode. To encode a file: base64 file.txt. On macOS the decode flag is -D (uppercase) rather than --decode.

In Windows PowerShell, Base64 encoding and decoding uses the .NET Convert class. To encode: [Convert]::ToBase64String([Text.Encoding]::UTF8.GetBytes("hello")). To decode: [Text.Encoding]::UTF8.GetString([Convert]::FromBase64String("aGVsbG8=")). PowerShell base64 decode is also used for the -EncodedCommand flag, which accepts a UTF-16 LE Base64-encoded command string. To decode a PowerShell encoded command use UTF-16 LE rather than UTF-8: [Text.Encoding]::Unicode.GetString([Convert]::FromBase64String($encoded)).

How Base64 encoding works

Base64 converts binary data by grouping every three bytes (24 bits) into four 6-bit values. Each 6-bit value maps to one of 64 printable ASCII characters: uppercase A-Z (0-25), lowercase a-z (26-51), digits 0-9 (52-61), plus (62), and slash (63). If the input length is not a multiple of three, the output is padded with one or two = signs to make the total length a multiple of four characters. This is why Base64 strings always end with 0, 1, or 2 equal signs.

URL-safe Base64 replaces + with - and / with _ to avoid conflict with URL reserved characters. The padding = character is sometimes omitted in URL contexts. This variant is used in JWTs, OAuth 2.0 tokens, and many web API authentication schemes. Base64 is not encryption and provides no security. For generating secure random values, the password generator uses crypto.getRandomValues() which is cryptographically secure. For protecting actual data, the text encryptor provides passphrase-based encryption rather than mere encoding.