ASCII to Base64

Encode ASCII text to a Base64 string for use in HTTP headers, API credentials, Basic Auth tokens, and configuration values. Handles standard ASCII characters and warns when input goes beyond the ASCII range.

Last updated: May 28, 2026

ASCII text input

URL-safe(uses - _ instead of + /)

Base64 output

Common use: encode username:password for an HTTP Basic Auth header. Base64 is encoding, not encryption — always transmit over HTTPS.

Client-Side Processing

Input Data Stays on Device

Instant Local Execution

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What is ASCII to Base64?

ASCII to Base64 encoding converts plain ASCII text — letters, numbers, and standard punctuation — into a Base64 string that is safe to transmit through any text-based channel. This is one of the most common encoding operations in web development, used in HTTP Basic Auth, API key encoding, JWT generation, and data URI construction.

ASCII is the 128-character subset of Unicode covering English letters, digits, and common symbols. Base64 encodes those bytes into a 64-character alphabet (A–Z, a–z, 0–9, +, /) with optional = padding. The result is safe for use in HTTP headers, JSON values, and URL parameters (with URL-safe mode).

How to Use ASCII to Base64

Type or paste your ASCII text into the input field

Click "Encode to Base64" to generate the encoded output

Enable URL-safe mode if the result will appear in a URL or filename

Copy the Base64 string for use in your API request, header, or config

Common Use Cases

Developers generating the credential block for HTTP Basic Authentication headers (username:password → Base64).
Engineers encoding API keys or tokens before embedding them in environment variables or config files.
Frontend developers creating data URIs for small inline text assets.
Security testers encoding payloads for manual HTTP request crafting in Burp Suite or curl.
QA engineers verifying Base64 encoding behavior in authentication and API testing workflows.

Example Input and Output

Encoding a username:password pair for an HTTP Basic Auth header — one of the most frequent ASCII to Base64 use cases.

ASCII text

deploy-bot:gh_token_abc123XYZ

Base64 output

ZGVwbG95LWJvdDpnaF90b2tlbl9hYmMxMjNYWVo=

Not encryption

Base64 is trivially reversible. Never use it to protect credentials or sensitive data. Always transmit Basic Auth over HTTPS.

Size overhead

Base64 output is approximately 33% larger than the ASCII input due to the 3-bytes-to-4-characters encoding ratio.

Frequently Asked Questions

What is ASCII to Base64 used for?

The most common use is HTTP Basic Authentication: the client encodes "username:password" to Base64 and sends it as the Authorization header value. It is also used for encoding API keys and short config strings.

What happens if my text contains non-ASCII characters?

Base64 encoding works on bytes, not characters, so the tool will still encode non-ASCII input. However, the receiving system may not decode it correctly if it expects ASCII-only content. A warning is shown when non-ASCII characters are detected.

Is the output different from Text to Base64?

For purely ASCII input the output is identical. The difference is intent: this tool targets the ASCII encoding use case and warns about non-ASCII input, while Text to Base64 is designed for general UTF-8 content.

When should I use URL-safe Base64?

Enable URL-safe mode when the encoded string will appear in a URL query parameter, a cookie, or a filename. URL-safe Base64 replaces + with - and / with _ to avoid conflicts with URL syntax.

Is my text sent to a server?

No. Encoding happens entirely in your browser. Your text never leaves your device.