The builds we know are listed here. There can be a gap between them as we didn't got a confirmation of that build. Sometimes Microsoft puts a gap for a reason, they do this to prepare one build for a public release.. Windows 8.1 9600.16384 - 21 August 16:23 (Official RTM, Public) Pre-Release to Manufacturing 9483 - 9 August 20:20 9444 - 3 August 07:36 9471 - 26 July 20:04 Milestone Preview 9431 - 15 June 12:14 9422 - 5 June 17:35 9418 - 30 May 19:05 9416 - 28 May 18:32 9415 - 25 May 08:45 9410 - 22 May 16:35 Milestone 2 9405 - 10 May 23:30 9403 - 9 May 20:0 9402 - 7 May 17:20 9400 - 6 May 20:30 (fbl_sfs_dev1_pr) 9391 - 26 April 20:00 9385 - 26 March 08:47 (fbl_uip_dev2) 9385 - 15 April 20:49 9379 - 10 April 07:11 9374 - 29 March 23:55 Milestone 1 9369 - 24 March 13:00 9364 - 15 March 21:05 9347 - 20 February 15:04 9345 - 18 February 17:36 9319 - ?? January 18:20 9314 - 2? January ??:?? 9304 - ?? January ??:?? 9300 - ?? January ??:?? Post-Release to Manufacturing 9289 - 20 December 20:22 9278 - ?? December ??:?? 9220 - ?? November ??:?? Windows 8.0 9200.16384 - 25 July 12:47 (Official RTM, Public) 8888.16384 - 24 July 15:55 (Unknown, Private) Pre-Release to Manufacturing 8523 - 22 July 18:15 (RTM Candidate) 8522 - 21 July 16:42 (RTM Candidate) 8521 - 20 July 18:44 (RTM Candidate) 8520 - 19 July 18:15 (RTM Candidate) 8519 - 18 July 19:00 (RTM Candidate) 8518 - 17 July 18:13 (RTM Candidate) 8517 - 16 July 18:05 (RTM Candidate) 8516 - 13 July 19:00 (RTM Candidate) 8515 - 12 July 19:00 (RTM Candidate) 8514 - 11 July 19:00 (RTM Candidate) 8513 - 10 July 19:00 (RTM Candidate) 8512 - 9 July 19:00 (RTM Candidate) 8511 - 8 July 12:20 (RTM Candidate) 8510 - 6 July 19:00 (RTM Candidate) 8509 - 5 July 19:00 (RTM Candidate) 8508 - 3 July 19:00 (RTM Candidate) 8507 - 2 July 19:00 (RTM Candidate) 8506 - 30 June 19:00 (RTM Candidate) 8505 - 29 June 19:00 (RTM Candidate) 8504 - 28 June 19:00 (RTM Candidate) 8503 - 27 June 19:05 (RTM Candidate) 8502 - 26 June 19:05 (RTM Candidate) 8501 - 25 June 19:04 (RTM Candidate) 8500 - 23 June 17:07 (RTM Candidate) 8500 - 19 June 20:00 8440 - 21 June 19:32 8439 - 20 June 19:16 8438 - 19 June 18:56 8437 - 18 June 13:25 8436 - 15 June 18:16 8431 - 6 June 20:00 8427 - 1 June 18:08 8424 - 29 May 18:55 8423 - 25 May 18:30 8422 - 25 May 19:23 (Computex RT Build) 8422 - 24 May 18:48 8421 - 23 May 17:40 8420 - 22 May 18:44 8419 - 21 May 18:35 8418 - 18 May 12:30 8415 - 8 May 19:00 8413 - ? May ??:?? 8411 - 2 May 18:01 Release Canidate: 8400 - 18 May 14:23 (Release Preview) 8385 - 17 May 17:25 8384 - 16 May 19:34 8383 - 15 May 18:32 8382 - 14 May 18:33 8381 - 13 May 10:08 8379 - 9 May 19:00 8378 - 8 May 19:52 8377 - 7 May 19:03 8376 - 6 May 09:20 8375 - 4 May 19:00 (Consumer Preview Update 2) 8373 - 2 May 19:00 8372 - 1 May 19:00 8371 - 30 April 19:23 8370 - 28 April 13:35