diff --git a/README.md b/README.md
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--- a/README.md
+++ b/README.md
@@ -1,9 +1,9 @@
 # image-triangles
 ### examples
 ![Sierra mountains original](examples/sierra.jpg)
-![Sierra mountains post-filter](examples/sierra-result.avif)
+![Sierra mountains post-filter](examples/sierra-result.webp)
 ![Dog original](examples/luna.jpeg)
-![Dog post-filter](examples/luna-result.avif)
+![Dog post-filter](examples/luna-result.webp)
 
 ### to run:
 
@@ -11,5 +11,5 @@ Install [cabal & ghc](https://www.haskell.org/ghcup/) if you don't have them.
 
 ```
 cabal update
-cabal run image-triangles -- --cornerCount 1000 --input examples/sierra.jpg --output output.avif
+cabal run image-triangles -- --cornerCount 1000 --input examples/sierra.jpg --output output.png
 ```
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