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General Settings

These settings control runtime behavior, error image styling, default output formats, and metadata handling. Most can be left at their defaults, but a few — like the error background color — are worth customizing for your environment.

DIMS_ERROR_BACKGROUND​

Sets the background color of the error image.

  • Default: #5adafd

This color will appear when an error image is generated, which can happen when:

  • The source image could not be downloaded
  • The image could not be processed (e.g., invalid format or size)
  • The server is under memory or resource pressure

Think of it as the visual "error signal" for go-dims. When you see this image, it’s usually a sign to check your logs.

note

mod_dims allowed setting a NOIMAGE fallback file — go-dims no longer supports that. Error images are now generated dynamically using libvips.

DIMS_STRIP_METADATA​

Enables or disables automatic removal of image metadata (EXIF, profiles, etc.).

  • Default: true

Stripping metadata is recommended for privacy, security, and cache efficiency. However, in use cases like DAM (Digital Asset Management), you may want to retain this data.

To disable globally:

DIMS_STRIP_METADATA=false

You can also override this per-request using the strip command.

DIMS_INCLUDE_DISPOSITION​

Controls whether to include the Content-Disposition header in image responses.

  • Default: false

When enabled, the response will include:

Content-Disposition: inline; filename=<filename>

To trigger downloads instead of inline display, you can append download=1 to the request URL. This changes the header to:

Content-Disposition: attachment; filename=<filename>

DIMS_DOWNLOAD_TIMEOUT​

Sets the maximum time (in milliseconds) an origin image download is allowed before being cancelled.

  • Default: 3000

Example:

DIMS_DOWNLOAD_TIMEOUT=5000

DIMS_DEFAULT_OUTPUT_FORMAT​

Specifies the default image format to convert to when no format is explicitly requested.

  • Default: (unset)

Example:

DIMS_DEFAULT_OUTPUT_FORMAT=webp

This is useful if you want all images to be served in a modern format by default. If a format is explicitly requested via the URL (e.g. using a format command), it takes precedence.

DIMS_OUTPUT_FORMAT_EXCLUDE​

Specifies a comma-separated list of image formats that should not be converted by the default output format setting.

  • Default: (unset)

Example:

DIMS_OUTPUT_FORMAT_EXCLUDE=GIF,SVG

This allows certain image types (like animated GIFs or vector SVGs) to bypass the default format conversion logic.