{"id":103430,"date":"2020-02-11T07:00:00","date_gmt":"2020-02-11T15:00:00","guid":{"rendered":"http:\/\/devblogs.microsoft.com\/oldnewthing\/?p=103430"},"modified":"2020-09-11T15:13:46","modified_gmt":"2020-09-11T22:13:46","slug":"20200211-00","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20200211-00\/?p=103430","title":{"rendered":"Survey of Windows update formats: The Delta update"},"content":{"rendered":"

Last time, we began our survey of Windows update formats<\/a>. We’ll continue with the Delta update.<\/p>\n

The Delta update<\/b> is a cut-down version of the Full update by including only files that changed since the previous version. Delta updates are typically around 300MB<\/a> to 500MB in size, which is significantly less than the typical 1GB size of a Full update.<\/p>\n

Delta updates send full files, not patches. The Delta<\/i> is applied at the file level, not the byte level.<\/p>\n\n\n\n\n\n\n\n\n\n
Update<\/th>\nFull file<\/th>\nPatch base<\/th>\n<\/tr>\n
M0<\/th>\nM1<\/th>\nM2<\/th>\nM3<\/th>\nM4<\/th>\n<\/tr>\n
M1<\/th>\n\n
M1<\/div>\n<\/td>\n
M0 to M1<\/span><\/td>\n\u00a0<\/td>\n\u00a0<\/td>\n\u00a0<\/td>\n\u00a0<\/td>\n<\/tr>\n
M2<\/th>\n\n
M2<\/div>\n<\/td>\n
M0 to M2<\/span><\/td>\nM1 to M2<\/span><\/td>\n\u00a0<\/td>\n\u00a0<\/td>\n\u00a0<\/td>\n<\/tr>\n
M3<\/th>\n\n
\u00a0<\/div>\n<\/td>\n
\u00a0<\/td>\n\u00a0<\/td>\n\u00a0<\/td>\n\u00a0<\/td>\n\u00a0<\/td>\n<\/tr>\n
M4<\/th>\n\n
M4<\/div>\n<\/td>\n
M0 to M4<\/span><\/td>\nM1 to M4<\/span><\/td>\nM2 to M4<\/span><\/td>\n\u00a0<\/td>\n\u00a0<\/td>\n<\/tr>\n
M5<\/th>\n\n
M5<\/div>\n<\/td>\n
M0 to M5<\/span><\/td>\nM1 to M5<\/span><\/td>\nM2 to M5<\/span><\/td>\n\u00a0<\/td>\nM4 to M5<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The breakdown of files for Delta updates is as follows:<\/p>\n\n\n\n\n\n\n\n\n
Delta update<\/th>\nContents<\/th>\n<\/tr>\n
M1<\/th>\nM1<\/td>\n<\/tr>\n
M2<\/th>\nM2<\/td>\n<\/tr>\n
M3<\/th>\n(nothing)<\/td>\n<\/tr>\n
M4<\/th>\nM4<\/td>\n<\/tr>\n
M5<\/th>\nM5<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Note that Delta update M3 contains nothing at all. That’s because the file F<\/code> didn’t change between M2 and M3, so there was nothing to update.<\/p>\n

Feature summary of Delta updates:<\/p>\n