Thanks for your updates on m4a seeking About 403 errors I have encountered 403 error with some youtube videos (before version 1.12.3, not sure when this appeared, but still here with 1.13) (most work and don't have this issue). Here is a dump of requests made (using a http proxy) on the video https://www.youtube.com/watch?v=8OqHjfS_vpA&hl=en on which I have this error : GET [url=https://www.youtube.com/watch?v=8OqHjfS_vpA&hl=en]https://www.youtube.com/watch?v=8OqHjfS_vpA&hl=en[/url] ← 200 text/html 42.17kB 483ms GET [url=http://s.ytimg.com/yts/jsbin/player-en_US-vflXJM_5_/base.js]http://s.ytimg.com/yts/jsbin/player-en_US-vflXJM_5_/base.js[/url] ← 200 text/javascript 1.06MB 5.79s GET [url=https://manifest.googlevideo.com/api/manifest/dash/requiressl/yes/playback_host/r4---sn-25g7sn76.googlevideo.com/mt/1450480874/mn/sn-25g7sn76/nh/IgpwcjAzLnBhcjEwKgkxMjcuMC4wLjE/key/yt6/]https://manifest.googlevideo.com/api/manife...C4wLjE/key/yt6/[/url] hfr/1/as/fmp4_audio_clear%2Cwebm_audio_clear%2Cfmp4_sd_hd_clear%2Cwebm_sd_hd_clear%2Cwebm2_sd_hd_clear/fexp/9416126%2C9420452%2C9422596%2C9423662/ip/2.90.0.189/mv/m/pl/16/ipbits/0/ms/a u/source/youtube/expire/1450502532/mm/31/id/o-AL8AFxycEDus8-jP2cRo8LY7-AkcVgXTtCsc5D_AAXi5/itag/0/upn/mhwp-clGZng/sver/3/signature/51FD1F2B2408FD4DDB98F97E8109F9769DA7F55C1D8.B10F16B920 50B31A0D5357D26A69C052FD67B8C68C6/sparams/as%2Chfr%2Cid%2Cip%2Cipbits%2Citag%2Cmm%2Cmn%2Cms%2Cmv%2Cnh%2Cpl%2Cplayback_host%2Crequiressl%2Csource%2Cexpire ← 403 text/html 2.16kB 76ms HEAD [url=https://r4---sn-25g7sn76.googlevideo.com/videoplayback?initcwndbps=2078750&requiressl=yes&mt=1450480874&keepalive=yes&nh=IgpwcjAzLnBhcjEwKgkxMjcuMC4wLjE&key=yt6&gir=yes&mime=audio%2Fwe]https://r4---sn-25g7sn76.googlevideo.com/vi...mime=audio%2Fwe[/url] bm&clen=3442346&fexp=9416126%2C9420452%2C9422596%2C9423662&lmt=1449647557852591&source=youtube&mv=m&pl=16&ipbits=0&mn=sn-25g7sn76&ms=au&ip=2.90.0.189&expire=1450502532&mm=31&id=o-AL8A FxycEDus8-jP2cRo8LY7-AkcVgXTtCsc5D_AAXi5&itag=171&upn=mhwp-clGZng&dur=219.601&sver=3&sparams=clen%2Cdur%2Cgir%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Ckeepalive%2Clmt%2Cmime%2Cmm%2Cmn %2Cms%2Cmv%2Cnh%2Cpl%2Crequiressl%2Csource%2Cupn%2Cexpire&signature=44AD4A7A5B02DD775DF8E1A61CF494195ACE1C31E3B.AD7FE6BB8C086E981F60F1B4B121C4938339976576 5 ← 403 text/plain [no content] 98ms HEAD [url=https://r4---sn-25g7sn76.googlevideo.com/videoplayback?initcwndbps=2078750&requiressl=yes&mt=1450480874&keepalive=yes&nh=IgpwcjAzLnBhcjEwKgkxMjcuMC4wLjE&key=yt6&gir=yes&mime=audio%2Fwe]https://r4---sn-25g7sn76.googlevideo.com/vi...mime=audio%2Fwe[/url] bm&clen=3442346&fexp=9416126%2C9420452%2C9422596%2C9423662&lmt=1449647557852591&source=youtube&mv=m&pl=16&ipbits=0&mn=sn-25g7sn76&ms=au&ip=2.90.0.189&expire=1450502532&mm=31&id=o-AL8A FxycEDus8-jP2cRo8LY7-AkcVgXTtCsc5D_AAXi5&itag=171&upn=mhwp-clGZng&dur=219.601&sver=3&sparams=clen%2Cdur%2Cgir%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Ckeepalive%2Clmt%2Cmime%2Cmm%2Cmn %2Cms%2Cmv%2Cnh%2Cpl%2Crequiressl%2Csource%2Cupn%2Cexpire&signature=44AD4A7A5B02DD775DF8E1A61CF494195ACE1C31E3B.AD7FE6BB8C086E981F60F1B4B121C4938339976576 5 ← 403 text/plain [no content] 105ms HEAD [url=https://r4---sn-25g7sn76.googlevideo.com/videoplayback?initcwndbps=2078750&requiressl=yes&mt=1450480874&keepalive=yes&nh=IgpwcjAzLnBhcjEwKgkxMjcuMC4wLjE&key=yt6&gir=yes&mime=audio%2Fwe]https://r4---sn-25g7sn76.googlevideo.com/vi...mime=audio%2Fwe[/url] bm&clen=3442346&fexp=9416126%2C9420452%2C9422596%2C9423662&lmt=1449647557852591&source=youtube&mv=m&pl=16&ipbits=0&mn=sn-25g7sn76&ms=au&ip=2.90.0.189&expire=1450502532&mm=31&id=o-AL8A FxycEDus8-jP2cRo8LY7-AkcVgXTtCsc5D_AAXi5&itag=171&upn=mhwp-clGZng&dur=219.601&sver=3&sparams=clen%2Cdur%2Cgir%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Ckeepalive%2Clmt%2Cmime%2Cmm%2Cmn %2Cms%2Cmv%2Cnh%2Cpl%2Crequiressl%2Csource%2Cupn%2Cexpire&signature=44AD4A7A5B02DD775DF8E1A61CF494195ACE1C31E3B.AD7FE6BB8C086E981F60F1B4B121C4938339976576 5 ← 403 text/plain [no content] 108ms HEAD [url=https://r4---sn-25g7sn76.googlevideo.com/videoplayback?initcwndbps=2078750&requiressl=yes&mt=1450480874&keepalive=yes&nh=IgpwcjAzLnBhcjEwKgkxMjcuMC4wLjE&key=yt6&gir=yes&mime=audio%2Fwe]https://r4---sn-25g7sn76.googlevideo.com/vi...mime=audio%2Fwe[/url] bm&clen=3442346&fexp=9416126%2C9420452%2C9422596%2C9423662&lmt=1449647557852591&source=youtube&mv=m&pl=16&ipbits=0&mn=sn-25g7sn76&ms=au&ip=2.90.0.189&expire=1450502532&mm=31&id=o-AL8A FxycEDus8-jP2cRo8LY7-AkcVgXTtCsc5D_AAXi5&itag=171&upn=mhwp-clGZng&dur=219.601&sver=3&sparams=clen%2Cdur%2Cgir%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Ckeepalive%2Clmt%2Cmime%2Cmm%2Cmn %2Cms%2Cmv%2Cnh%2Cpl%2Crequiressl%2Csource%2Cupn%2Cexpire&signature=44AD4A7A5B02DD775DF8E1A61CF494195ACE1C31E3B.AD7FE6BB8C086E981F60F1B4B121C4938339976576 5 ← 403 text/plain [no content] 56ms HEAD [url=https://r4---sn-25g7sn76.googlevideo.com/videoplayback?initcwndbps=2078750&requiressl=yes&mt=1450480874&keepalive=yes&nh=IgpwcjAzLnBhcjEwKgkxMjcuMC4wLjE&key=yt6&gir=yes&mime=audio%2Fwe]https://r4---sn-25g7sn76.googlevideo.com/vi...mime=audio%2Fwe[/url] bm&clen=3442346&fexp=9416126%2C9420452%2C9422596%2C9423662&lmt=1449647557852591&source=youtube&mv=m&pl=16&ipbits=0&mn=sn-25g7sn76&ms=au&ip=2.90.0.189&expire=1450502532&mm=31&id=o-AL8A FxycEDus8-jP2cRo8LY7-AkcVgXTtCsc5D_AAXi5&itag=171&upn=mhwp-clGZng&dur=219.601&sver=3&sparams=clen%2Cdur%2Cgir%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Ckeepalive%2Clmt%2Cmime%2Cmm%2Cmn %2Cms%2Cmv%2Cnh%2Cpl%2Crequiressl%2Csource%2Cupn%2Cexpire&signature=44AD4A7A5B02DD775DF8E1A61CF494195ACE1C31E3B.AD7FE6BB8C086E981F60F1B4B121C4938339976576 5 ← 403 text/plain [no content] 55ms