Base64, Hex & ASCII Converter

Convert firmware blobs between base64, hex and raw bytes, with size and checksum readouts.

Example: 5 bytes: 48656C6C6F — CRC-32 0xF7D18982.

Inputs

Input

Whitespace is ignored. URL-safe base64 (- and _) is accepted.

Input format

Result

Base64

SGVsbG8=

Hexadecimal: 48656C6C6F
ASCII: Hello
Bytes: 5
CRC-32: 0xF7D18982
Base64 length: 8 chars

Base64 encodes 3 bytes as 4 characters, so 5 bytes become 8 characters — 60% larger. That overhead is the price of surviving text-only transports.
100% of these bytes are printable ASCII, so this is probably text rather than a binary blob.
CRC-32 of the decoded bytes is 0xF7D18982. Comparing that against the source is a faster check than eyeballing the encoding — and it catches truncation, which base64 padding often hides.

First bytes

Offset	Hex	Decimal	ASCII
0	48	72	H
1	65	101	e
2	6C	108	l
3	6C	108	l
4	6F	111	o

/* generated by urdb.io/tools/base64-hex */
static const uint8_t data[5] = {
    0x48, 0x65, 0x6C, 0x6C, 0x6F,
};

Check it against real silicon

Chiprun runs your firmware on an emulated microcontroller and hands back the UART output, so you can confirm these numbers rather than trusting them.

Chiprun docs

Formula

base64 packs 3 bytes into 4 characters — a 33% size increase

Worked example

5 bytes: 48656C6C6F — CRC-32 0xF7D18982.

base64 packs 3 bytes (24 bits) into 4 six-bit characters
5 bytes → ceil(5/3) × 4
8 characters
Trailing = signs pad the final group when the length is not a multiple of three.

Frequently asked questions

Why is base64 33% larger than the original?

Because it represents 3 bytes (24 bits) using 4 characters of 6 bits each. That is the cost of restricting the output to a safe printable alphabet, which is what lets binary data survive email, JSON and other text-only transports.

What do the trailing equals signs mean?

Padding. Base64 works in 3-byte groups, so when the data does not divide evenly the final group is padded — one = for two leftover bytes, two = for one. Some decoders accept base64 without padding; some do not.

What is URL-safe base64?

The same encoding with - and _ replacing + and /, because those two characters have meaning in URLs and filenames. This tool accepts either on input. Padding is often omitted in the URL-safe form too.

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