What is Namecoin's blocksize limit? Bitcoin's blocksize limit is currently 1MB. It seems as if Namecoin would have to be bigger due to it proving 512 bytes of storage with a name update, but it also has slower average block times (about 20 minutes according to BitInfoCharts). 

Does Namecoin also have block size limit? What size is it?
Namecoin has not strayed from Bitcoin in this parameter, it is still set at a 1 MB block size limit. You can find it in main.h:

/** The maximum allowed size for a serialized block, in bytes (network rule) */
static const unsigned int MAX_BLOCK_SIZE = 1000000;