Editing Aztec Code (section)

=== Bit stuffing ===
The data bits are broken into codewords, with the first bit corresponding to the most significant coefficient.  While doing this, code words of all-zero and all-ones are avoided by [[bit stuffing]]: if the first ''b''−1 bits of a code word have the same value, an extra bit with the complementary value is inserted into the data stream.  This insertion takes place whether or not the last bit of the code word would have had the same value or not.

Also, note that this only applies to strings of ''b''−1 bits ''at the beginning of a code word''.  Longer strings of identical bits are permitted as long as they straddle a code word boundary.

When decoding, a code word of all zero or all one may be assumed to be an [[erasure code|erasure]], and corrected more efficiently than a general error.

This process makes the message longer, and the final number of data codewords recorded in the mode message is not known until it is complete.  In rare cases, it may be necessary to jump to the next-largest symbol and begin the process all over again to maintain the minimum fraction of check words.