Guide #1

Convert video format with FFmpeg

Format conversion is often about the container, codec, or both. The safest default for broad playback is H.264 video, AAC audio, and an MP4 container.

Copy + paste this:

Re-encode to a broadly compatible H.264/AAC MP4.

ffmpeg -i input -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k -movflags +faststart output.mp4

When this is the right tool

Start by checking whether this operation matches the job you actually need.

Use this when

3 Good fit

A file plays locally but fails in a browser or mobile app.
Users upload MOV, MKV, AVI, or WebM and your product needs one standard output.
You need predictable files for downstream editing, playback, or storage.

Be careful when

2 Watch out

You only need to change the file extension. That can corrupt expectations.
You can stream-copy safely and do not need a codec change.

Examples

Use these as starting points, then tune quality, size, and timing on real input files.

Safe MP4 output

Re-encode to a broadly compatible H.264/AAC MP4.

ffmpeg -i input -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k -movflags +faststart output.mp4

Command breakdown

input input: Reads this input file.
-c:v libx264: Sets the video codec.
-crf 23: Controls visual quality. Lower values make larger, higher-quality files.
-preset medium: Controls encode speed and compression efficiency.
-c:a aac: Sets the audio codec.
-b:a 128k: Sets the audio bitrate.
-movflags +faststart: Moves MP4 metadata to the front so web playback can start sooner.
output output.mp4: Writes this output file.

Fast remux

Change container without re-encoding when streams are already compatible.

ffmpeg -i input -c copy -movflags +faststart output.mp4

Command breakdown

input input: Reads this input file.
-c copy: Copies streams without re-encoding.
-movflags +faststart: Moves MP4 metadata to the front so web playback can start sooner.
output output.mp4: Writes this output file.

Helpful tips

These details prevent most bad outputs and confusing FFmpeg results.

Container is not codec

MP4, MOV, and MKV are containers. H.264, H.265, VP9, and AV1 are codecs. You may need to change one or both.

Use stream copy when possible

If the codecs already work in the target container, `-c copy` avoids quality loss and runs very fast.

Use faststart for web MP4

`-movflags +faststart` moves playback metadata near the start of the file, so browsers can begin sooner.

Related guides

Useful next steps when this operation is part of a larger workflow.

Compress video with FFmpeg

Learn practical FFmpeg video compression using CRF, presets, bitrate caps, and web-safe MP4 settings.

Resize video with FFmpeg

Learn how to resize video with FFmpeg while keeping aspect ratio, avoiding odd dimensions, and padding when needed.

Need to run this at scale?

Run the same FFmpeg commands through a hosted API.

Keep the FFmpeg command surface. Very Good FFmpeg handles machines, logs, long jobs, outputs, and webhooks.

Try free Read API docs

Guide #1

Convert video format with FFmpeg

Format conversion is often about the container, codec, or both. The safest default for broad playback is H.264 video, AAC audio, and an MP4 container.

Copy + paste this:

Re-encode to a broadly compatible H.264/AAC MP4.

ffmpeg -i input -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k -movflags +faststart output.mp4

When this is the right tool

Start by checking whether this operation matches the job you actually need.

Use this when

3 Good fit

A file plays locally but fails in a browser or mobile app.
Users upload MOV, MKV, AVI, or WebM and your product needs one standard output.
You need predictable files for downstream editing, playback, or storage.

Be careful when

2 Watch out

You only need to change the file extension. That can corrupt expectations.
You can stream-copy safely and do not need a codec change.

Examples

Use these as starting points, then tune quality, size, and timing on real input files.

Safe MP4 output

Re-encode to a broadly compatible H.264/AAC MP4.

ffmpeg -i input -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k -movflags +faststart output.mp4

Command breakdown

input input: Reads this input file.
-c:v libx264: Sets the video codec.
-crf 23: Controls visual quality. Lower values make larger, higher-quality files.
-preset medium: Controls encode speed and compression efficiency.
-c:a aac: Sets the audio codec.
-b:a 128k: Sets the audio bitrate.
-movflags +faststart: Moves MP4 metadata to the front so web playback can start sooner.
output output.mp4: Writes this output file.

Fast remux

Change container without re-encoding when streams are already compatible.

ffmpeg -i input -c copy -movflags +faststart output.mp4

Command breakdown

input input: Reads this input file.
-c copy: Copies streams without re-encoding.
-movflags +faststart: Moves MP4 metadata to the front so web playback can start sooner.
output output.mp4: Writes this output file.

Helpful tips

These details prevent most bad outputs and confusing FFmpeg results.

Container is not codec

MP4, MOV, and MKV are containers. H.264, H.265, VP9, and AV1 are codecs. You may need to change one or both.

Use stream copy when possible

If the codecs already work in the target container, `-c copy` avoids quality loss and runs very fast.

Use faststart for web MP4

`-movflags +faststart` moves playback metadata near the start of the file, so browsers can begin sooner.

Related guides

Useful next steps when this operation is part of a larger workflow.

Compress video with FFmpeg

Learn practical FFmpeg video compression using CRF, presets, bitrate caps, and web-safe MP4 settings.

Resize video with FFmpeg

Learn how to resize video with FFmpeg while keeping aspect ratio, avoiding odd dimensions, and padding when needed.

Need to run this at scale?

Run the same FFmpeg commands through a hosted API.

Keep the FFmpeg command surface. Very Good FFmpeg handles machines, logs, long jobs, outputs, and webhooks.

Try free Read API docs