Where hex turns up in operations
Hexadecimal is the lingua franca of anything close to the metal: MAC addresses, IPv6 addresses, memory addresses in kernel oopses, escape sequences in logs (\x1b[0m), color codes, packet dumps from tcpdump -X, and byte offsets in hexdump output. When a log line contains \x48\x54\x54\x50 and you want to know what a client actually sent, hex-to-text answers it in one paste (that one is HTTP).
Text ↔ hex conversion
The converter is UTF-8 aware in both directions: text is encoded to UTF-8 bytes before being rendered as hex, and decoded hex is interpreted as UTF-8. It tolerates the formats you actually meet in the wild, spaced pairs (48 65 6c), continuous strings, and 0x-prefixed values, by stripping everything that is not a hex digit before decoding.
Base conversion with BigInt
The number converter uses JavaScript's BigInt, so it handles values far beyond 253 without silently losing precision, useful for converting large IDs, memory addresses from a 64-bit stack trace, or feature-flag bitmasks. Type 0x or 0b prefixes and it detects the base automatically.
Three conversions worth memorising anyway
Even with a converter one paste away, some equivalences are worth knowing cold: 0xff = 255 (a full byte, the maximum of each IPv4 octet), 0x7f = 127 (the ASCII boundary; anything above it isn't plain ASCII), and each hex digit maps to exactly four bits, which is why a /24 netmask 255.255.255.0 is 0xffffff00. For everything else (particularly IPv6 math and long bitmasks) use the tool and save your brain for the actual outage.