Base64 Encoder Decoder
100% privateFree online Base64 encoder decoder — encode text to Base64 and decode Base64 strings instantly. 100% browser-based, no data sent to servers.
Base64 is a binary-to-text encoding scheme that converts binary data into a sequence of 64 printable ASCII characters. This free online Base64 encoder takes any plain text or binary data and instantly outputs the corresponding Base64-encoded string — no server calls, no uploads. Whether you need a Base64 encoder for embedding images in CSS data URIs, encoding credentials for HTTP Basic Auth headers, or preparing binary data for JSON payloads, this tool handles it in milliseconds.
The online Base64 decoder works in the opposite direction: paste any valid Base64 string and the tool decodes it back to the original text or reveals the underlying data. A common use case is decoding JWT payload sections, which are URL-safe Base64-encoded JSON objects. The Base64 encoder decoder also supports URL-safe mode (replacing + with − and / with _), making it the right tool for working with JWTs, cookie values, and URI components.
Unlike many online Base64 encoder decoder tools, this tool runs entirely in your browser using the native TextEncoder and atob/btoa APIs. Nothing is ever sent to a server. Your credentials, tokens, and file contents stay on your machine. There is no account, no tracking, and no request size limit — just a fast, private Base64 encoder and decoder that works every time.
How It Works
- Paste your plain text or Base64 string into the input area
- Select Encode to convert text to Base64, or Decode to reverse the process
- Toggle URL-safe mode if your output will be used in URLs, JWT headers, or filenames
- Click Copy to copy the result — your data never leaves the browser
Features
- Encode plain text to Base64 instantly
- Decode Base64 strings back to readable text
- URL-safe Base64 mode (replaces + and / with - and _)
- One-click copy to clipboard
- Works with text of any length — no size limits
- 100% client-side: no server, no uploads, no tracking
Examples
Encode plain text
Input
Hello, Developer!Output
SGVsbG8sIERldmVsb3BlciE=Decode Base64 string
Input
eyJhbGciOiJIUzI1NiJ9Output
{"alg":"HS256"}Decode JWT header (URL-safe Base64)
Input
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9Output
{"alg":"HS256","typ":"JWT"}Common Use Cases
- Encoding API credentials for HTTP Basic Authentication headers (Authorization: Basic ...)
- Decoding JWT header and payload sections to inspect algorithm and claims
- Embedding images as Base64 data URIs in HTML, CSS, or email templates
- Encoding binary attachment content for JSON or XML REST APIs
- Debugging Base64-encoded cookie, session, or OAuth token values
Developer Tips
- JWTs use URL-safe Base64 without padding — toggle URL-safe mode and strip trailing = signs before decoding a JWT segment
- Standard Base64 always ends in 0, 1, or 2 = padding characters; missing padding is the most common decode failure
- If you need to pass Base64 in a URL query string, always use URL-safe mode — + is interpreted as a space by servers
- Base64 increases data size by ~33% — for large payloads, consider gzip compression before encoding
Frequently Asked Questions
- What is a Base64 encoder?
- A Base64 encoder is a tool that converts binary or text data into a Base64-encoded string using 64 printable ASCII characters (A–Z, a–z, 0–9, +, /). Base64 encoding is used whenever binary data needs to travel through a channel that only supports text — such as HTTP headers, JSON payloads, email attachments, and data URIs. An online Base64 encoder like this one performs the conversion entirely in your browser with no server involved.
- What is a Base64 decoder?
- A Base64 decoder reverses the Base64 encoding process, converting a Base64-encoded string back into its original text or binary data. Developers use a Base64 decoder to inspect JWT tokens, decode API credentials, read email attachment content, and debug Base64-encoded values in cookies or OAuth flows. This free online Base64 decoder runs client-side — your data never leaves your machine.
- What is the best Base64 decoder tool?
- The best Base64 decoder tool is one that is fast, private, and works entirely in the browser without sending your data to a server. This tool encodes and decodes Base64 instantly using native browser APIs, supports URL-safe Base64 (required for JWTs), works with text of any length, and requires no login or installation. Your input is never transmitted or stored.
- When should I use Base64 encoding?
- Use Base64 when you need to transmit binary data over a medium that only supports text, such as embedding an image in a data URI (data:image/png;base64,...), storing binary data in JSON or XML, encoding credentials in HTTP Basic Authentication headers, or passing binary payloads through APIs that expect JSON.
- Does Base64 compress my data?
- No. Base64 encoding increases data size by approximately 33% because every 3 bytes of binary data are represented by 4 ASCII characters. It is an encoding scheme, not a compression algorithm. If you need to reduce size, compress first (e.g., with gzip) and then Base64-encode the compressed result.
- Is Base64 the same as encryption?
- No. Base64 is not encryption and provides zero security. Anyone can decode a Base64 string instantly with any free online Base64 decoder. It is simply a way to represent binary data as text. Do not use Base64 to hide or protect sensitive data — use proper encryption algorithms like AES for that purpose.
- What is URL-safe Base64?
- Standard Base64 uses + and / characters which have special meaning in URLs. URL-safe Base64 replaces + with - and / with _ so the encoded string can be used safely in URLs and filenames without percent-encoding. JWTs use URL-safe Base64 (without the trailing = padding). Always use URL-safe mode when encoding values that will appear in query strings, path segments, or HTTP cookie values.