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Base64 Explained: Encode, Decode, Images, Base64URL and the Size Cost

How much bigger Base64 makes data, how Base64URL differs, and when a data URL for an image is worth it.

URL-safe (Base64URL: - and _ , no padding)

Result

The Base64 appears here as you type.

Base64 is an encoding, not encryption: anyone can decode it. Everything here runs in your browser and nothing is uploaded.

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📚 Official sources: Base64 standard (RFC 4648)

We build every tool from the official rules and re-check them when they change. Always confirm with the official source before you rely on a result.

🛠️ Spotted a mistake or an out-of-date rule? Tell us

How much bigger Base64 makes data

Base64 turns every 3 bytes into 4 text characters, so encoded data is about a third larger. It's an encoding, not encryption: anyone can decode it.

Original	Base64 length	Size increase
3 bytes	4 characters	+33%
100 bytes	136 characters	+36%
1 KB	1,368 characters	+34%
10 KB	13,656 characters	+33%
100 KB	136,536 characters	+33%
1 MB	1,398,104 characters	+33%

Base64URL swaps + and / for - and _ and usually drops the = padding, so it's safe in URLs and file names; JWTs use it. Inlining an image as a data URL saves a request but adds about 33% to its size and can't be cached separately, so it only pays off for small icons.

Base64 Decode: Turn Base64 Back Into Text

Paste Base64 and get the text back, with full UTF-8 and emoji support. URL-safe Base64 works too. Nothing is uploaded.

Base64 Encode Text Online

Turn any text into Base64 with UTF-8 support. Copy it in one tap. Free and private.

Image to Base64: Data URL, <img> Tag and CSS

Convert an image into a Base64 data URL, ready to paste into HTML or CSS. Runs in your browser.

Base64 to Image: Preview and Download

Paste Base64 image data, see the picture and download it as PNG, JPG, GIF, WebP or SVG.

Base64URL Encode (URL-Safe Base64)

Encode text as URL-safe Base64 with - and _ and no padding, as used in JWTs and web addresses.

Questions people ask

What is Base64?+

Base64 turns any data, such as text, an image or a file, into plain letters and numbers (A–Z, a–z, 0–9, + and /). It is used to put images inside HTML or CSS, to send files in email and JSON, and in tokens such as JWTs.

Is Base64 encryption?+

No. Anyone can decode Base64 in a second, so never use it to hide passwords or secrets. It only changes the format of the data.

What is Base64URL?+

A version that is safe inside web addresses and file names: + becomes -, / becomes _, and the = padding at the end is dropped. JWTs use it. This decoder reads both kinds automatically.

Does it work with emoji and other languages?+

Yes. Text is encoded as UTF-8, the standard used on the web, so emoji, accents, Arabic, Urdu, Hindi and every other script come back exactly the same.

Base64

Base64 Decode Base64 Encode Text Image to Base64