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In WordPress, a post thumbnail is the same post-level assignment that WordPress calls a Featured image. Open the post, display the settings sidebar, choose Featured image, select or upload an image in the Media Library, and click Set featured image. Whether readers actually see it—and where—depends on your theme and its templates.
Set a featured image in the block editor
- Open the post or page. From the WordPress dashboard, open Posts (or Pages) and edit the item.
- Open settings. Click the gear or settings icon in the upper-right corner if the sidebar is hidden. Make sure you are viewing the post/page settings, not only the settings for a selected block.
- Find Featured image. In the post or page settings sidebar, locate Featured image. You can drag an image into its box, or click Set featured image.
- Choose the image. Select an existing file in the Media Library, or use the upload option to add a new file. Confirm with Set featured image.
- Save your work. Click Save draft, Update, or Publish. Use the post preview and, when appropriate, the archive or home-page preview to check the result.
You can replace the assignment later by choosing a different image, or remove it from the same Featured image panel. Assigning an image here is different from inserting an image into the article body: the first associates a file with the post itself, while the second adds an Image block at a particular point in the content.
Assign an image that is already in the post
If the image is already inserted in the article, you do not need to upload it again.
- Click the image’s Image block.
- Open the block’s More options menu (the three-dot control).
- Choose Set as featured image.
- Save or update the post.
This produces the same post-level featured-image assignment as selecting a file from the settings sidebar. The practical difference is only where you start: the Media Library route begins with a file choice, while this route begins with an image already in the content.
Why the image may not appear on your site
Setting the assignment does not force every theme to render it. WordPress documentation notes that many themes use the image on a home page or blog index, but a particular theme may show it in a header, archive card, search result, single-post layout, or nowhere at all. A block theme can render it through a template containing a Post Featured Image block.
Check the theme template
If the editor shows a Featured image but the public page does not, inspect the template used by the post and its archive. In a block theme, open the Site Editor and look for a Post Featured Image block in the relevant single-post or archive template. In a classic theme, the theme’s PHP templates determine whether the assigned image is output. A plugin or custom post type can also alter the available controls.
When the control is missing
If Featured image is absent from the sidebar, first open the settings sidebar and confirm that you are editing the post/page itself. Then check whether the current content type and theme support post thumbnails. WordPress themes must declare that support; a site administrator or theme developer may need to enable it. The exact fix depends on the theme and content type, so do not assume that changing an image setting will restore a missing control.
Image size, crop, and quality
There is no universal WordPress featured-image pixel size that guarantees the right result. Themes request registered image sizes such as Thumbnail, Medium, Large, or Full Size, and themes can register additional sizes. A registered size may be proportionally scaled or cropped; a crop can also specify a focal position. The same source file can therefore look different in a hero banner, archive card, and single-post header.
Choose for the actual layout
- Use an image with the subject visible near the center when you do not know the theme’s crop position.
- Prefer a sufficiently large original so the theme does not enlarge a small file.
- Check the post preview and at least one archive or home-page view at desktop and mobile widths.
- Keep important text, faces, or logos away from edges that a thumbnail crop may remove.
These are practical checks, not a WordPress rule. The correct dimensions come from the active theme’s templates and registered sizes. Media settings may control some generated sizes, but changing them does not necessarily change a theme’s custom crop or an already-generated file.
Displaying the assignment in a block template
The Post Featured Image block is a rendering tool, not another way to assign the image. In a block-based template, add or select that block where the image should appear, then configure the controls your theme supports.
- Link to post: makes the image open the post.
- Alignment: controls placement in the template’s content area.
- Aspect ratio and dimensions: constrain the displayed box.
- Border and image style: change presentation when supported by the theme.
If no image is assigned, the block may be empty or display a theme-defined fallback. Template changes affect where assigned images render; they do not replace the assignment step in the post editor.
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Common problems and fixes
The image is set but missing from the home page
Confirm that the home-page or archive template actually renders a Post Featured Image block (or equivalent theme output). Some themes intentionally omit featured images from certain views. Clear any page-cache or optimization layer only after confirming the template and assignment.
The image appears but is cropped badly
Preview the layout at its real card or header ratio. Choose a source with safer margins, adjust the focal composition in an image editor, or change the template’s aspect-ratio/crop setting if the theme exposes one. Avoid assuming that uploading a larger file alone will change the crop.
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The wrong image is shown
Reopen the post’s Featured image panel and verify the assigned attachment. If the public page still shows an older file, check whether an archive or CDN cache is serving a previous rendition. Also inspect whether a custom template uses a different image field.
The sidebar or Featured image panel is hidden
Click the upper-right settings icon, exit distraction-free or full-screen editing if enabled, and switch from block settings to post/page settings. If the panel remains unavailable, investigate theme or post-type support rather than the image file.
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Check the file type and size accepted by your WordPress installation, your hosting limits, and available Media Library storage. An administrator may need to adjust server limits or permissions. Do not delete the existing featured image until the replacement upload succeeds.
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If you need screenshots of a WordPress post, preview, or archive for documentation or QA, ScreenshotNeo can capture a URL through one GET request. It accepts consent banners before capture and removes more than 60 known consent platforms, newsletter popups, and chat widgets; each cleanup step can be disabled. Bot checks or CAPTCHAs, blank pages, timeouts, failed loads, and cache hits are not billed, and response headers identify the page verdict and billing result. Its MCP server provides take_screenshot, get_page_info, and capture_pdf tools for Claude, Cursor, and other MCP clients.
See the complete parameter reference in the ScreenshotNeo documentation. The following examples use the service’s required access key and capture a WordPress URL; replace the URL with your own preview or public post.
cURL
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://example.com/your-post -o shot.webpPython
import requests
r = requests.get("https://api.screenshotneo.com/v1/shot", params={"access_key": "YOUR_API_KEY", "url": "https://example.com/your-post"}, timeout=90)
r.raise_for_status()
open("shot.webp", "wb").write(r.content)Node.js
const q = new URLSearchParams({ access_key: 'YOUR_API_KEY', url: 'https://example.com/your-post' });
const res = await fetch(`https://api.screenshotneo.com/v1/shot?${q}`);
if (!res.ok) throw new Error(`HTTP ${res.status}`);
const fs = await import('node:fs/promises');
await fs.writeFile('shot.webp', Buffer.from(await res.arrayBuffer()));ScreenshotNeo offers 1,000 screenshots a month free with no card. Paid plans start at $5 for 3,000 shots; every feature is included on every plan. Create a free ScreenshotNeo account.
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Is a post thumbnail different from a featured image?
In this WordPress context, “post thumbnail” and “featured image” describe the same post-level image assignment. “Featured image” is the label used in the current editor.
Can I assign a featured image without displaying it in the article?
Yes. The assignment is independent of an Image block in the body. Your theme may still use it in archives, social metadata, or other templates.
Will changing the featured image alter the original Media Library file?
No. It changes which attachment is associated with the post. The underlying media file remains in the Media Library unless you separately edit or delete it.
Frequently Asked Questions
Can one image be the featured image for several posts?
Yes. The same Media Library attachment can be assigned to multiple posts; assigning it does not remove it from any other post.
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Not necessarily. Social cards depend on your theme and SEO or social-sharing plugin, which may use the featured image or another configured image.
The Bottom Line
Use the post settings sidebar to assign the image, or use an existing Image block’s Set as featured image action. Then verify the theme template and real archive or post preview, because WordPress does not guarantee where—or whether—the assignment is displayed.
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