diff --git a/README.md b/README.md
index 73d0f9205..2126ec474 100644
--- a/README.md
+++ b/README.md
@@ -51,11 +51,11 @@ Screenshots
 <tr valign="bottom">
 <td width = 50%>
 
-<img src="https://github.com/OHDSI/PatientLevelPrediction/raw/main/vignettes/sparseCalibration.png" alt="Calibration plot" title="Calibration plot" />
+<img src="https://github.com/OHDSI/PatientLevelPrediction/raw/main/vignettes/sparseCalibration.webp" alt="Calibration plot" title="Calibration plot" />
 
 </td>
 <td width = 50%>
-<img src="https://github.com/OHDSI/PatientLevelPrediction/raw/main/vignettes/sparseROC.png" alt="ROC plot" title="ROC plot" />
+<img src="https://github.com/OHDSI/PatientLevelPrediction/raw/main/vignettes/sparseROC.webp" alt="ROC plot" title="ROC plot" />
 
 </td>
 </tr><tr>