The first frame of an APNG file is stored as a normal PNG stream, so most old PNG decoders are able to display the first frame of an APNG file. The frame speed data and extra animation frames are stored in extra chunks (as provided for by the original PNG specification). Some web browsers cannot display APNG files due to incompatibility. APNG competes with MNG, a powerful format for bitmapped animations created by the same team as PNG. APNG's advantage is the smaller library size and compatibility with older PNG implementations. The file extension is .apng or .png.