CRC Lookup Table Generator

About CRC Lookup Tables

Computing a CRC one bit at a time means shifting a register and conditionally XORing the polynomial for every single bit of input — correct, but slow when you're processing large buffers. A CRC lookup table trades a small amount of memory for a large amount of speed: it precomputes the CRC contribution of every possible byte value (256 entries for the classic byte-wise algorithm) so each input byte can be resolved with a single table lookup and XOR instead of eight separate shift-and-branch steps.

This is why lookup tables are the standard technique in firmware, device drivers, network stacks, and file format libraries — anywhere a CRC has to run over kilobytes or megabytes of data without burning CPU cycles. The table generated here is derived from the exact width, polynomial, and reflection settings currently configured in the calculator above, so it matches your chosen algorithm rather than a generic default.

Need it as ready-to-use source instead of a raw table? The Code Generator turns this same table into a static array plus an update function in C, Python, or JavaScript — including the initial value and final XOR step, which are easy to forget when hand-rolling a lookup-based implementation from scratch.