How to Calculate Steam ID for Non-Steam Games using JavaScript


const target = '"C:\\Program Files (x86)\\Origin\\Origin.exe"';
const label = 'Fubar Game';

const top32 = BigInt.asUintN(32, BigInt(require('crc').crc32(target + label)));
const bottom32 = 0x02000000n;
const steamId = (top32 << 32n) | bottom32;

// 7673385367021551616

Note: You can remove the Node.js dependency on the crc package by replacing require('crc').crc32(...) with any CRC32 implementation (example).

The Steam ID is a 64-bit unsigned integer. The top 32 bits are the CRC32 checksum of the concatenated target and label UTF-8 encoded strings. The bottom 32 bits are the constant 0x02000000. So all you have to do is concat the strings, calculate the checksum, shift left 32 bits, and set the constant bits.

We cast everything to BigInt because JavaScript numbers cannot accurately represent 64-bit integers. We use BigInt.asUintN(32, ...) to ensure the checksum is an unsigned 32-bit integer (some CRC32 implementations return negative numbers).

The values of the target and label strings should exactly match the values in the Steam UI (include double quotes if and only if they appear in Steam).

Mike Moore

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Austin, TX
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