Image Preview

Display thumbnail previews of selected images before uploading. Enable with asp-thumbnails="true". Thumbnails are generated on the client side using the browser's native image APIs, so no server round-trip is required.

What you should see: a thumbnail for every selected image, generated locally before upload. Accepts the common image types up to 10 MB; non-images are refused.

Drag & drop files here, or paste from clipboard

<core-upload asp-upload-url="/api/upload/upload/multiple"
 asp-multiple="true"
 asp-extensions=".jpg,.jpeg,.png,.gif,.webp,.bmp"
 asp-max-size="10MB"
 asp-thumbnails="true"
 asp-auto-upload="true"
 asp-progress="true"
 asp-drop-zone="true"
 asp-button-text="Select Images">
</core-upload>

Seeing the file before it goes

asp-thumbnails is true by default and previews are generated in the browser, so nothing is uploaded to produce them and the queue fills in immediately.

The check that costs nothing

A preview is how the user notices they picked the wrong screenshot before waiting for it to upload. That matters most when several files are chosen at once — exactly when a mistake is easiest to make and hardest to spot in a list of names.

Each preview means decoding an image, so for a folder of hundreds turn thumbnails off and get a text queue that renders instantly.