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optimize is the one you reach for when you don’t want to think about settings. Point it at a directory, pick a preset, and it resizes and re-encodes everything inside — keeping each file’s existing format unless you say otherwise.

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Arguments

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string
required
The directory to optimize. Searched recursively for image files.

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Options

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string
default:"web"
Which preset to apply: web, social, or email. See the table below for what each one does.
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string
Convert everything to this format instead of keeping each file’s source format.
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string
Directory to write results into. Defaults to writing next to each input file — see the warning below for why you usually want to set this.
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boolean
default:"false"
Keep EXIF/XMP in the output. Metadata is stripped unless you pass this.
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boolean
deprecated
A no-op — metadata is already stripped by default. Accepted so the flag doesn’t error if you write it out of habit.
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string
Write a JSON report of the results to this path. Same shape as convert.
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boolean
default:"false"
Report what would be written without writing it.

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Presets

Images smaller than the preset’s limit aren’t scaled up — the limit is a ceiling, not a target.

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Two behaviours worth knowing

It recurses, and it will find its own previous output. Run optimize on a directory without --out and a second run picks up the files the first run created. Always write somewhere separate — bmux optimize photos --preset web --out optimized
Extensions get normalised. Keeping the source format means keeping the format, not the spelling — a .jpg input comes back as .jpeg, because that’s the canonical extension for image/jpeg. If you need the original spelling, use convert instead.

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Changing format at the same time

--to overrides the keep-source-format behaviour, so you can resize and convert in one pass:

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Checking first

Because optimize touches a whole directory, --dry-run is worth the habit:

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Files it can’t identify

Format is detected from file contents, not the extension. Anything that isn’t a supported image is reported as failed and the rest of the batch continues:
The command exits non-zero when anything failed.