what's different between package-archive and package-delta for apk file from google play

Question

 I download several apks from google play, some of them the content type == "archive", but some of them used "delta",  I saw the hex for both are not same, can someone give detail info regarding what's different?

mimeType="application/vnd.android.package-archive" Content-Type: application/vnd.android.package-delta

Thanks

Answer 1

I think application/vnd.android.package-delta is gzcompressed.

If you download an apk with content type = "application/vnd.android.package-delta" it's size is smaller as compared to the one with content type = "application/vnd.android.package-archive".

Like the whatsapp file size is 9.4mb and 14.7mb.

Yes the download links are different.

The one which returns the the delta at the end has this "apk_gz" in it's link that's why i think it's gzcompressed.

--Edit--
Just like Theo pointed out they are actually changes in the apk file. You can read about it here .

Answer 2

The greek letter delta is often used to mean change in both math and physics. So, a delta-package only records the parts in the .apk (or any other package like .rpm (rpmdelta) or .deb (debdelta)) that actually have changed. Because of this one can't install new software from a delta-package. However when updating apps only downloading the changes makes sense, as the download is smaller. To further reduce filesize, a delta-package can also be packed, as said by Mehul.

I hope this helps.