Abstract: Described is an improved decoder that reduces the number of bounds checks needed for typical compressed data by first guaranteeing that there is sufficient room to decode small symbol substrings and literal symbols, whereby bounds checking need not be performed on each symbol. Because literal symbols and small substrings of symbols form the majority of compressed data, the reduced checking significantly speeds up decoding on average. In one implementation, a fast LZ77 decoder that operates without bounds checking is used in a first phase until the end of the output buffer is neared at which time a second phase standard decoder, which performs bounds checks on each to ensure that the buffer does not overflow, is used. Normally the standard decoder decompresses only a small amount of data relative to the amount of data decompressed with the fast decoder, greatly improving decompression speed while not compromising safety.