Encode and decode Base64 strings or binary files instantly. Supports URL-safe base64url, UTF-8 unicode, MIME line wrapping, Data URLs, and live error repair.
Encode and decode Base64 strings or binary files instantly. Supports URL-safe base64url, UTF-8 unicode, MIME line wrapping, Data URLs, and live error repair.
64-character mapping table assigned to 6-bit values from 0 to 63. Standard RFC 4648 uses [A-Za-z0-9+/], while URL-safe replaces + and / with - and _.
Suffix character added when the input binary stream is not a multiple of 24 bits. Adds == for 1 remainder byte, or = for 2 remainder bytes. Omitted in base64url.
Column count after which a CRLF or LF line break is inserted. MIME uses 76 characters per line, PEM uses 64 characters, and modern web APIs typically use None.
Byte serialization standard for plain text. UTF-8 handles all global Unicode characters and emojis. ISO-8859-1 (Latin-1) and ASCII restrict to single-byte ranges.
MIME-prefixed URI format (data:[<mediatype>][;base64],<data>) allowing images, fonts, audio, and documents to be embedded directly into HTML and CSS files.
The standard browser window.btoa() function throws an InvalidCharacterError when encountering any character outside the Latin-1 range (code point > 255). To safely encode modern UTF-8 text containing emojis or non-English scripts, convert the string into a Uint8Array using new TextEncoder().encode(str) before mapping the byte stream to Base64.
Standard Base64 contains the plus (+) and slash (/) characters. When passed in HTTP URL query parameters, web servers often decode + into a blank space, corrupting the payload. Always use the URL-safe Base64url specification (RFC 4648 §5) which substitutes + with - and / with _, and strips trailing = padding.
Embedding assets as Data URLs eliminates HTTP roundtrips, but Base64 expands binary file size by exactly 33.33% (4 characters for every 3 bytes) and prevents separate browser caching. Reserve inline Data URLs for tiny icons and critical SVGs under 4KB; keep larger media as external HTTP/2 or HTTP/3 cached resources.
If an API or log truncates trailing equals signs, determine the required padding using modulo arithmetic: calculate remainder = stringLength % 4. If remainder is 2, append ==. If remainder is 3, append =. If remainder is 1, the string is malformed because 6 bits cannot represent a complete 8-bit octet.
The input string contains characters outside the Base64 alphabet (such as spaces, line breaks, or URL percent-encoded characters like %2B). Enable the Auto-Clean switch to strip whitespace and normalize hyphens/underscores, or verify whether the data was encoded with URL-safe base64url.
This is caused by an encoding mismatch. The original text was converted from UTF-8 multi-byte bytes, but the decoder is reading them as ISO-8859-1 (Latin-1), or vice versa. Change the Text Character Encoding selector from Latin-1/ASCII to UTF-8 to restore the proper multi-byte character reconstruction.
Base64 groups 6 bits into characters; an encoded length with a remainder of 1 mod 4 means there are only 6 bits available, which is insufficient to reconstruct even a single 8-bit byte. This proves the string was cut off during network transmission or copy-pasting. Retrieve the complete payload from the source.
Base64 encoding converts every 3 bytes (24 bits) of binary input into 4 ASCII characters (each representing 6 bits). Because each output character is stored as an 8-bit ASCII byte in memory and over HTTP, 24 bits of input become 32 bits of output. This produces a constant mathematical ratio of 4/3, resulting in exactly a 33.33% increase in data size before line breaks and padding.
Standard Base64 (RFC 4648 §4) uses + and / as its 62nd and 63rd characters and uses = for padding. In URL query strings and filenames, + is interpreted as a space and / acts as a path delimiter. Base64url (RFC 4648 §5) replaces + with hyphen (-) and / with underscore (_), and typically omits the trailing = padding characters to ensure safe URL and filename transmission without URL-encoding.
The native browser btoa() function was created for binary strings where each character code point must fit in a single 8-bit byte (0 to 255). Modern Unicode characters (such as emojis, accented letters, or Asian scripts) require 2 to 4 bytes in UTF-8. Passing a code point higher than 255 violates btoa specifications. Modern applications must first serialize the string to UTF-8 bytes using TextEncoder before Base64 conversion.
To display a Base64 image in HTML or CSS without an external file, prepend the appropriate media type prefix and base64 marker: data:image/[format];base64,[data]. For example, a PNG image uses data:image/png;base64,iVBORw0KGgo... You can paste this entire string directly into the src attribute of an HTML <img> tag or inside a CSS background-image: url(...) property.
Base64 padding using the equals sign (=) should be omitted when generating JSON Web Tokens (JWTs), OAuth access tokens, and URL slugs governed by the RFC 7515 (JWS) and RFC 4648 §5 specifications. Because the length of the string is known by the parser, the missing bits can be mathematically calculated (string.length % 4), making padding redundant and saving URL space.
Convert JSON payloads into clean, strongly typed TypeScript interfaces or type aliases with automatic nested object inference and union detection.
Infer and generate TypeScript Zod schemas, type definitions, and nested validation rules from raw JSON payloads.
Convert JSON structures into high-performance TypeBox Type.Object definitions for Fastify, Ajv, and TypeScript runtime validation.
Transform JSON data into lightweight, tree-shakable Valibot schema definitions with v.object, v.string, v.number, and array validators.
Transform raw JSON payloads into production-ready Python Pydantic v2 BaseModel classes, TypedDict, or standard @dataclass schemas with type hints and alias support.
Convert JSON objects into idiomatic Go (Golang) struct definitions with automatic type inference, nested struct decoupling, and customizable struct tags.