How do I check which formats my ImageMagick supports?

Run magick -list format. Each line ends with read, write and multi-image flags. A format missing from the list was not compiled into your build.

Why can ImageMagick read HEIC but not write it?

The format shows r-- meaning read-only. Writing HEIC needs an encoder that many distributions omit, often for patent reasons around HEVC.

How do I add WebP support to ImageMagick?

Support is compiled in, so you need a different build. On macOS use Homebrew, on Alpine add the imagemagick-webp package, or use the official AppImage. Alternatively convert with cwebp directly.

no encode delegate for this image format (AVIF, HEIC, WebP)

Format support is compiled into ImageMagick, not enabled by a flag. How to check what your build supports and install a build that includes the format you need.

convert: no encode delegate for this image format `WEBP' @ error/constitute.c/WriteImage/1265
convert: no decode delegate for this image format `HEIC' @ error/constitute.c/ReadImage/575

What it means

ImageMagick does not implement most codecs itself. It links against external libraries — libwebp, libheif, libjxl, libraw — at compile time. If your binary was built without one, no command-line flag can add it. The support is either in the binary or it is not.

Check what you have

magick -list format | grep -iE 'webp|heic|avif|jxl'

  WEBP* WEBP      rw-   WebP Image Format (libwebp 1.3.2)
  HEIC  HEIC      r--   High Efficiency Image Format

The three characters are read, write and multi-image support. In that example WebP can be read and written, HEIC can only be read. A format missing from the list entirely is not supported at all.

Also useful:

magick -version          # the DELEGATES line lists compiled-in libraries
magick -list delegate     # external programs it can shell out to

Getting a build with the format

macOS

brew install imagemagick

Homebrew's build includes WebP, HEIC and AVIF. If you installed a long time ago, brew upgrade imagemagick.

Debian / Ubuntu

The stock imagemagick package is often missing HEIC and sometimes AVIF. Install the extra delegates:

apt install imagemagick libmagickcore-6.q16-6-extra
apt install libheif1 libheif-plugin-libde265     # HEIC/AVIF decoding

If that is not enough, the AppImage from imagemagick.org is a fully-featured IM7 build with no compiling:

wget https://imagemagick.org/archive/binaries/magick
chmod +x magick
./magick -list format | grep -i heic

Alpine

apk add imagemagick imagemagick-heic imagemagick-webp imagemagick-jpeg

Alpine splits every delegate into its own package, so a bare apk add imagemagick supports almost nothing. This catches a lot of people building small Docker images.

Format-specific notes

HEIC — needs libheif. Reading iPhone photos also requires an HEVC decoder such as libde265; some distributions omit it for patent reasons, which is why HEIC often shows as unsupported even with libheif present.
AVIF — needs libheif built with libaom or a comparable AV1 codec. Encoding is slow; expect several seconds for a large photo.
JPEG XL — needs libjxl and a recent ImageMagick. Support is still uneven across distributions.
RAW (CR2, NEF, ARW) — delegated to dcraw or libraw, which are separate installs.

Workarounds when you cannot change the build

# WebP via the reference encoder
cwebp -q 80 input.png -o output.webp
dwebp input.webp -o output.png

# HEIC via libheif's own tools
heif-convert input.heic output.jpg

# AVIF via libavif
avifenc --min 20 --max 30 input.png output.avif

Convert with the dedicated tool, then hand the result to ImageMagick for everything else. In a pipeline this is often faster anyway.