Base64 writes binary data with 64 printable characters: A to Z, a to z, 0 to 9, + and /, with = as padding. It dates from the PEM mail standard of 1987, was fixed in MIME in 1993 and is specified in RFC 4648. It exists so that bytes can travel through systems built for text, such as email and JSON.

How does Base64 encoding work?

Three bytes are 24 bits, split into four groups of six bits, each written as one of the 64 characters. The output is a third larger than the input. When the input isn't a multiple of three bytes, the last group is padded with one or two = characters so the length is a multiple of four.

What is Base64 used for?

Email attachments (MIME), data URLs in HTML and CSS, JSON Web Tokens, HTTP Basic authentication headers, images inlined in stylesheets, binary fields in JSON and XML, and the SSH and PEM key files on every developer's machine.

Not the standard alphabet: + and / have meanings in a URL and = is reserved, so they have to be percent-encoded. The URL-safe variant from RFC 4648 §5 swaps them for - and _ and usually drops the padding; JWTs and most web APIs use it. The encoder here offers both.

How does Base64 compare to the other encodings?

It is the default for a reason: a third larger than the bytes, where hex doubles them and Base85 adds a quarter; built into every language and browser (btoa, atob, Buffer); and understood by every protocol. Pick Base32 when case can't be trusted, Base58 for things people copy by hand, Base85 only where PDF or PostScript asks for it.

Can Base64 be used for encryption?

No. Base64 is an encoding, not encryption: it changes how bytes are written, not who can read them, and anyone can decode it with no key. Encrypt first (AES, age, a library's sealed box) when the content needs protecting, then encode the ciphertext if it has to travel as text.

How do I convert a file to Base64?

Drop the file onto the input or choose it with the button. Its bytes are encoded in your browser and the Base64 appears in the result pane, with the size it grew to. Copy it, or download it as a text file.

How big a file can I convert?

Any file the browser can hold in memory works; a few hundred megabytes is fine, and the result is a third larger.

What do I do with the Base64?

Whatever needs the bytes as text: a data URL (`data:image/png;base64,…`), a JSON field, an email attachment or a config value. Base64 is safe in a URL only in its URL-safe variant, and it is a third larger than the file, so it is for carrying bytes through text, not for storing them.

Is my file uploaded anywhere?

Nothing leaves your browser. The file is read into memory on your machine and the encoding is computed there, in plain JavaScript; the page makes no request with it. Load the page, go offline and it keeps working.

File to Base64.

Drop any file and get its Base64, ready for a data URL or a JSON field. The bytes are encoded in your browser, so a 10 MB image takes a moment and never leaves your machine.64 characters+33% size4:3 characters to bytes0 bytes uploaded

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Drop any file onto the input or choose one with the button; it is read on your machine.
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The bytes are encoded as Base64 and the result shows how much larger the text is.
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Copy the Base64 into your code or config, or download it as a text file.

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For personal projects & open source

$32instead of $49/mo

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Client work, SaaS products and anything you charge for.Commercial use: Personal & open source only
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Complete multi-page sites you can ship as they are.Templates: All 14 templates
React icons from every major library, installable with one command.React icons: 294k+ icons
Presets that restyle every block, in light and dark.Themes: All 59 themes
Lets your AI editor search, preview and install blocks for you.MCP server: Basic usage
Priority requests are answered first.Support: Standard

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For companies with larger teams

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File to Base64.

File to Base64.

How it works

Drop a file

Read the result

Copy or download

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Questions and answers

What is Base64?

How does Base64 encoding work?

What is Base64 used for?

Is Base64 URL-safe?

How does Base64 compare to the other encodings?

Can Base64 be used for encryption?

How do I convert a file to Base64?

How big a file can I convert?

What do I do with the Base64?

Is my file uploaded anywhere?

Build the product around it