og:image tag can be used to specify the URL of the image that appears when someone shares the content to Facebook. The full list of image properties can be found here.
When content is shared for the first time, the Facebook crawler will scrape and cache the metadata from the URL shared. The crawler has to see an image at least once before it can be rendered. This means that the first person who shares a piece of content won't see a rendered image:
There are three ways to avoid this and have images render on the first Like or Share action:
Pre-cache the image with the Sharing Debugger: Run the URL through the URL debugger to pre-fetch metadata for the page. This can also be used to update the image for a piece of content.
Pre-cache the image using Graph API: Perform a force-scrape of the URL programmatically using the Graph API to pre-fetch metadata for the page . This can also be used to update the image for a piece of content.
og:image:height Open Graph tags:
Using these tags will specify the image dimensions to the crawler so that it can render the image immediately without having to asynchronously download and process it.
We cache all images referenced based on each image's URL, so if you replace an image:
Note that updating the image for a URL will not automatically update the preview for old shares. To do this, you must refresh the share as described here.
If you have any problems with images not being displayed correctly for a URL, try plugging in the image URL in the Sharing Debugger for any errors. If you think there's an issue on our side, consider filing a bug report to us.