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Encoding video for the web

Encoding Video


Install FFmpeg with homebrew. You'll need to install it with a couple flags for webm and the AAC audio codec.

brew install ffmpeg --with-libvpx --with-libvorbis --with-fdk-aac --with-opus

If you already have ffmpeg installed, but not with the other libraries, use the reinstall command.

brew reinstall ffmpeg --with-opus

FFmpeg options. The -c:v option is an alias for -vcodec and -c:a is an alias for -acodec. -crf is Constant Rate Factor.

Constant Rate Factor

This method allows the encoder to attempt to achieve a certain output quality for the whole file when output file size is of less importance. This provides maximum compression efficiency with a single pass. Each frame gets the bitrate it needs to keep the requested quality level. The downside is that you can't tell it to get a specific filesize or not go over a specific size or bitrate.

Convert to MP4

When converting to an MP4, you want to use the h264 video codec and the aac audio codec because IE11 and earlier only support this combination. The FFmpeg and H.264 Encoding Guide can walk you through some of the H.264 specific options.

ffmpeg -i -vcodec h264 -acodec aac -strict -2 output.mp4

For maximum compatibility, use the profile option. This may, however, increase the bit rate quite a bit. You can disable the audio stream with the -an option. -pix_fmt yuv420p is for Apple Quicktime support.

In this example, is converted to output.mp4 with maximum compatibility, with Quicktime support, and without an audio stream.

ffmpeg -an -i -vcodec libx264 -pix_fmt yuv420p -profile:v baseline -level 3 output.mp4

Convert to WebM


libvpx is the VP8 video encoder for ​WebM. FFmpeg and WebM Encoding Guide will walk you through webm specifics.

In this example, is converted to output.webm with a constant rate factor of 10 (lower is higher quality) at a bitrate of 1M. Changing the bitrate to something lower (e.g. 700K) will result in lower file sizes and lower quality. If your video does not have audio, you may leave off the -acodec libvorbis part.

ffmpeg -i -vcodec libvpx -qmin 0 -qmax 50 -crf 10 -b:v 1M -acodec libvorbis output.webm


VP9 can encode videos at half the file size 😄👏 You can check out Google's VP9 encoding guide for their recommend settings or the FFmpeg VP9 guide.

Here's an example from the FFmpeg guide:

ffmpeg -i -vcodec libvpx-vp9 -b:v 1M -acodec libvorbis output.webm

And here's Google's "Best Quality (Slowest) Recommended Settings". You need to run the first line(s). It will create a log file (and warn you the out.webm is empty). On the second pass, the video will be output.

ffmpeg -i <source> -c:v libvpx-vp9 -pass 1 -b:v 1000K -threads 1 -speed 4 \
  -tile-columns 0 -frame-parallel 0 -auto-alt-ref 1 -lag-in-frames 25 \
  -g 9999 -aq-mode 0 -an -f webm /dev/null

ffmpeg -i <source> -c:v libvpx-vp9 -pass 2 -b:v 1000K -threads 1 -speed 0 \
  -tile-columns 0 -frame-parallel 0 -auto-alt-ref 1 -lag-in-frames 25 \
  -g 9999 -aq-mode 0 -c:a libopus -b:a 64k -f webm out.webm


As of January 2015, all major browsers support MP4.

Data current as of October 2017. Sources:

Browser H264 H265 VP8 VP9 AAC MP3 VORBIS OPUS
Chrome for Desktop 30 - 30 30 30 30 30 33
Chrome for Android 30 - 30 30 30 30 30 -
IE 9 101 - - 9 9 - -
IE Mobile 10 - - - 10 10 - -
Edge 12 121 - 142 12 12 - 14
Firefox for Desktop 22 - 20 28 22 22 20 20
Firefox for Android 20 - 20 28 20 20 20 20
Safari for Mac 3 113 - - 3 3 - -
Safari for iOS 3 113 - - 3 3 - -
Opera for Desktop 25 - 11 16 - - 11 12
Android Stock Browser 2.3 - 4.0 5 2.3 2.3 4.0 -


  1. Supported only for devices with hardware support.
  2. Edge 14+ has partial support for VP9
  3. Supported only on macOS High Sierra.

Recommended markup

Since all browsers support MP4, we can use WebM's VP9 codec for modern browsers and fall back to MP4s for the rest.

  <source src="path/to/video.webm" type="video/webm; codecs=vp9,vorbis">
  <source src="path/to/video.mp4" type="video/mp4">

Creating thumbnail images from the video

Here's their guide. Output a single frame from the video.

ffmpeg -i input.mp4 -ss 00:00:14.435 -vframes 1 out.png

Output one image every second as a jpg.

ffmpeg -i input.mp4 -vf fps=1 out%3d.jpg

Reversing a video

FFmpeg now has a reverse filter. Usage: (source from this video.stackexchange answer)

For video only:

ffmpeg -i input.mp4 -vf reverse reversed.mp4

For audio and video:

ffmpeg -i input.mp4 -vf reverse -af areverse reversed.mp4

This filter buffers the entire clip. For larger files, segment the file, reverse each segment and then concat the reversed segments.


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AKin28 commented Aug 3, 2016

How to do this with ffmpeg? mp4 to images. 60FPS


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kn00tcn commented Jan 23, 2017

'ie for windows' also includes edge?


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jschertz commented Feb 12, 2017

This is an excellent resource. Thanks for throwing it together!


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cenobitedk commented Mar 11, 2017

This is a great guide, thank you!
However, I'm not impressed with the results compared to a h264 encoding. I'm encoding a 480p file for a website and the h264 encoding results in 20MB. My VP9 file looks awful when the filesize is less than 18MB. All I can read is that VP9 encoding should give me a filesize of down to 50% of the h264 file. Why can't I get near that at all?


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Vestride commented Mar 17, 2017

I updated the support table to include Edge.


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TrevorSundberg commented Apr 5, 2017

The -an command line argument has to go at the end right before the output file, otherwise it does nothing: -an output.mp4


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tvler commented May 8, 2017

Thanks for writing this up :)


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BryceLee commented May 13, 2017

How to convert mp4 to webp?


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resool commented May 25, 2017

nice tutorial!
just fyi: I didn't know what the -strict flag meant so I checked the docs and find out that:

Note: -strict experimental (or -strict -2) was previously required for this encoder, but it is ​no longer experimental and these options are unnecessary since 5 December 2015.



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ODonnellM commented Jul 24, 2017

Hey all, I made a little python wrapper to do exactly this in one easy command. I'd love for it to get some use and some feedback if anyone was looking for an open source solution to converting video files for the web.


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jeffpamer commented Aug 11, 2017

I've probably revisited this gist 20 times over the past year, so I thought I'd just say thanks for writing it up. It's incredibly useful.


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andreyrd commented Sep 8, 2017

Hey, I believe the brew install command should have the flag --with-fdk-aac, not --with-fdk-aacc. :)


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shshaw commented Sep 15, 2017

FYI: FFMPEG does have a reverse filter now:

ffmpeg -i <source> -vf reverse reversed.mp4

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shshaw commented Sep 15, 2017

I keep having issues when converting to webm and ogv, the color of the video drastically changes. Any suggestions?


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joeyhoer commented Sep 29, 2017

Will this post be updated with H265 documentation?


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Vestride commented Oct 20, 2017

Thanks for the notes, I've updated the install flag, updated the reverse a video section, and added H.265 for IE/Edge/Safari.


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jasonm commented Dec 12, 2017

For h.264, should this post also advise using -movflags faststart per this article about including the moov atom at the beginning of the file for efficient seeking?


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superhawk610 commented Jan 17, 2018

@jasonm shouldn't it be -movflags +faststart?


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AntonTrollback commented Feb 12, 2018

Thank you @Vestride


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Themanwithoutaplan commented Feb 20, 2018

Has anyone got a snippet for MP4 (AVC, AAC), VP9 and MP4 (HEVC)? I can't seem to come up with a combination that works: Safari will ignore the HEVC if the AVC is there.


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Baswazz commented Mar 20, 2018

Thank you for this great guide @Vestride


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denji commented Jul 7, 2018

Removed via ffmpeg metadata -map_metadata -1.


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MatthewZaso commented Oct 4, 2018

This guide is D O P E

One additional tip for anyone stuck:
I was trying to encode a video with an odd width value and was ending up with the following error:

width not divisible by 2 (61x58)

After some searching, I found this short command that when appended to the video adds a 1px padding to the video:
(Padding is preferable to scaling in this context to avoid distortion)

-vf pad="width=ceil(iw/2)*2:height=ceil(ih/2)*2"

from this StackOverflow post

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