john

Yes，only used on when put complete same files in archive，same in name and same in file content . yes，if different files renamed in same name ，its hard to identify them then.

To be honest，just used for store files，no need to extract files. Sometimes only extract one file of them for test.

Yes，Still thanks for this method . It is effective for Header size reducing .

hi Igor Pavlov： sorry to bother you again, can I ask you if you know some way to make a 7z archive which contains 1000 qty. a.txt file，each a.txt is same. Last time I made one but only by use 'rn' damand to change the file name inside the archive. and when the archive size is big, change the inside-name is not very quick. aIso I tried another way , put each a.txt in different folders ,but when compressing, the folders also go into the archive. could you share if you have better way ? thank you a...

hi Igor Pavlov： sorry to bother you again, can I ask you if you know some way to make a 7z archive which contains 1000 qty. a.txt file，each a.txt is same. Last time I made one but only by use 'rn' damand to change the file name inside the archive. aIso I tried another way , put each a.txt in different folders ,but when compressing, the folders also go into the archive. could you share if you have better way ? thank you again.

hi Igor Pavlov： Thanks alot for your opinion, you are right，I tried 1000 qty txt of 7z with same name and 1000 qty txt of 7z with differant name (name in order)，and even the length of the same name double，the header size is much less and it is visible. thanks

attached two txt about properties. the source file is too big, so only reserve begining info.

For better compare, now I creat a new archive named "new", for compared with old archive “old”。 old.7z has 100000 (number) txt file, each txt file is the same, each txt file size is 43 kb, new.7z has 100000 (number) txt file, each txt file is the same, each txt file size is 43 kb, old.7z header size is 845. Physical Size = 618888 new.7z header size is 38170. Physical Size = 656201 attached two txt about properties.