Base64 Encoder / Decoder
Encode and decode Base64 strings online. Free, no login.
Base64 encoding increases file size by ~33%. It was originally designed for email attachments in the 1980s!
How to use the Base64 Encoder / Decoder
Paste any plain text into the input panel and click Run (or press Ctrl+Enter) to instantly encode it to a Base64 string. Switch to Decode mode to reverse the process — paste a Base64 string and get the original text back. Use the Swap button to flip input and output without retyping.
Step-by-step guide
- 1 Paste your text
Type or paste the plain text you want to encode into the Input panel on the left.
- 2 Select mode
Make sure 'Encode →' is selected in the toolbar. Switch to '← Decode' if you want to reverse a Base64 string.
- 3 Click Run
Press the ⚡ Run button or use the keyboard shortcut Ctrl+Enter (Cmd+Enter on Mac).
- 4 Copy the result
Click the Copy button to copy the Base64 output to your clipboard instantly.
What can you do with this tool?
- Encode API secrets and tokens for HTTP Basic Auth headers
- Embed binary file contents in JSON or XML payloads
- Decode Base64-encoded JWT payload sections
- Encode image data for inline CSS data URIs
- Inspect Base64-encoded cookies or session tokens
- Prepare email attachments encoded in Base64 (MIME)
Why use STB's Base64 Encoder / Decoder?
STB's Base64 Encoder / Decoder is completely free — no account, no email, no credit card. It runs entirely in your browser so your data never leaves your device. Whether you're a developer, student, or just someone who needs a quick base64 encoder / decoder, open this tool and get results in seconds. No ads, no rate limits, no paywalls — just a fast, clean tool from Software That Benefits, a studio dedicated to free tools for developers and students.
Frequently Asked Questions
What is Base64 encoding?
Base64 is a binary-to-text encoding scheme that represents binary data using 64 printable ASCII characters (A–Z, a–z, 0–9, +, /). It is widely used to safely transmit binary data over text-based protocols like HTTP, email (MIME), and JSON.
Is Base64 the same as encryption?
No. Base64 is encoding, not encryption. Anyone can decode a Base64 string without a key — it provides no security. Use it only to safely represent binary data as text, not to hide sensitive information.
Does this tool send my data to a server?
Never. STB's Base64 tool runs entirely in your browser using the built-in btoa() and atob() JavaScript functions. Your text is never uploaded or stored anywhere.
Why does Base64 output end with == or =?
Base64 encodes data in 3-byte chunks. If the input length is not a multiple of 3, padding characters (=) are added to the end to complete the final chunk. One = means one byte of padding; == means two bytes.
What's the difference between standard Base64 and URL-safe Base64?
Standard Base64 uses + and / which are special characters in URLs. URL-safe Base64 replaces + with - and / with _ so the encoded string can be safely used in URLs and filenames without percent-encoding.
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