The Tool Desk
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Set a Featured Image (the WordPress thumbnail)
The quickest method works in the block editor for both posts and pages.
- Open Posts > All Posts or Pages > All Pages, then edit the item.
- Click the Settings (gear) icon in the upper-right if the sidebar is hidden.
- Choose the Post or Page settings tab—not the settings for an individual block.
- Find Featured image and click its image area.
- Choose an existing image from the Media Library, upload a file, or drag an image into the featured-image area.
- Select the image and click Set featured image.
- Click Save draft, Publish, or Update.
To change it later, open the same control and choose Replace. To clear it, choose Remove featured image. Assigning an image does not guarantee that every visitor will see it in the same place: the active theme decides whether it appears above the content, in an archive card, on the home page, or nowhere at all.
Why the image may not appear on the site
Featured images are data attached to the post or page. A theme must request and render that data in its templates. Two themes can use the same assigned image in different locations, crop it differently, or omit it entirely. Plugins and site-specific templates can also alter the output. Check a single post, an archive/listing page, and the home page to see which templates use the image.
Choose dimensions and understand WordPress image sizes
WordPress creates several derivative sizes when you upload an image. The built-in names include Thumbnail, Medium, Medium Large, Large, and Full Size. Administrators can review configurable dimensions at Settings > Media.
| WordPress size | Documented default or behavior | What it means |
|---|---|---|
| Thumbnail | 150 × 150 pixels, square-cropped by default | Useful for small archive cards; the crop can remove part of the subject. |
| Medium | Up to 300 × 300 pixels | WordPress scales within the maximum rather than forcing both dimensions. |
| Large | Up to 1024 × 1024 pixels | A larger derivative for article or hero layouts. |
| Full Size | The uploaded original | Can be much larger than the theme needs, increasing transfer size. |
These are documented defaults, not universal requirements. Your theme may register custom sizes and CSS may display a different crop. Do not assume that 150 × 150 is the right social-card size or that one dimension fits every theme and sharing service. Use a sharp source image with the important subject away from edges so alternative crops remain usable.
Changing sizes for a custom theme
Theme developers can define support and sizes in theme setup. set_post_thumbnail_size() registers the post-thumbnail size:
set_post_thumbnail_size( 1200, 675, true );The first two arguments are width and height. With true, WordPress crops to those dimensions; with false, it scales proportionally. An array can specify a crop position. For additional named derivatives, use add_image_size():
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Make a shared link show the intended thumbnail
A page’s on-site Featured Image and its social link-preview image are separate output paths. Social platforms read metadata emitted in the page’s HTML, commonly Open Graph fields. Your active SEO or social plugin may select the Featured Image, but selection and fallback rules are plugin-dependent.
Check the existing metadata provider first
- Identify the SEO or social-sharing plugin already active on the site.
- Open its social or Open Graph settings and confirm that the page’s Featured Image is eligible for sharing.
- View the page source and search for
og:imageand related tags. Confirm that the URL points to the image you expect. - Change the image in the post editor, update the page, and then allow the sharing service to fetch the revised metadata.
Do not install a second Open Graph plugin automatically. Multiple plugins can emit duplicate tags, leaving a platform to choose an unexpected value. One WordPress.org Open Graph plugin documents a typical order—Featured Image first, then images in post content and attachments, followed by site imagery such as the icon, custom logo, or header image—but that is that plugin’s behavior, not a guarantee for every site or social service. Sharing services can also retain an earlier preview, so a change may not appear immediately.
When a remote image is required
If the image lives outside your Media Library, a plugin that supports remote Featured Images can provide that workflow. Review its current documentation and compatibility with your theme and SEO plugin before enabling it; remote-image behavior is not part of WordPress core.
Troubleshoot missing controls, odd crops, and wrong previews
“Featured image” is missing
The editor sidebar varies by theme and plugins. First verify that you are viewing the Post or Page settings tab and that the sidebar is expanded. If the control is still absent, the active theme may not declare post-thumbnail support. A developer can add this during theme setup:
add_action( 'after_setup_theme', function () {
add_theme_support( 'post-thumbnails' );
} );Child themes and custom post types may need their own support and editor configuration. Test on a staging site before editing production theme files.
The thumbnail is unexpectedly cropped
Determine which derivative the template requests. A 150 × 150 square crop, a custom card size, and the original image will all look different. Inspect the rendered image URL or template code, then review Settings > Media and the theme’s registered sizes. Changing a setting affects newly generated derivatives; it does not resize every existing upload automatically. Regenerate derivatives after a deliberate size change and check the result at the actual display width.
The site shows one image but a shared link shows another
Inspect the page source for duplicate or conflicting Open Graph tags. Check the SEO/social plugin’s per-page image override, then confirm that the Featured Image is saved and publicly reachable. If the source is correct but a messaging app still shows an old image, its crawler may have cached the earlier metadata. Re-fetch behavior differs by service; avoid promising an instant refresh.
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The image is blurry or too heavy
Upload a sufficiently large original for the largest template that uses it, but avoid sending the Full Size file when a smaller derivative is available. Compress photographs, use a modern format when your stack supports it, and verify that responsive image markup is present. A tiny source enlarged by CSS cannot recover detail; an oversized original increases page weight.
Test both thumbnail paths before publishing
- Open the post at desktop and mobile widths.
- Check an archive, search result, and any related-post card where the theme may use a different size.
- View page source and confirm one intended
og:imagevalue. - Make sure the image URL is public, uses HTTPS, and does not require a login.
- After replacing an image, update the post and allow external preview caches to expire or re-fetch.
Or skip the browser setup
If you need a clean thumbnail of a live website rather than a WordPress Featured Image, ScreenshotNeo returns a PNG, JPEG, WebP, or PDF from one request. It accepts cookie and consent banners before capture and removes more than 60 known consent platforms, newsletter popups, and chat widgets. Bot checks, blank pages, timeouts, failed loads, and cache hits are not billed, and response headers identify the page verdict and billing status. Its MCP server lets Claude, Cursor, and other MCP clients call take_screenshot, get_page_info, and capture_pdf.
See the complete parameter reference in the ScreenshotNeo documentation. A direct cURL request is:
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpPython:
import requests
r = requests.get("https://api.screenshotneo.com/v1/shot", params={"access_key": "YOUR_API_KEY", "url": "https://stripe.com"}, timeout=90)
open("shot.webp", "wb").write(r.content)Node.js:
const q = new URLSearchParams({ access_key: 'YOUR_API_KEY', url: 'https://stripe.com' });
const res = await fetch(`https://api.screenshotneo.com/v1/shot?${q}`);ScreenshotNeo includes full-page capture, element selection, device presets, retina scale, dark mode, custom CSS and JavaScript, waits, request blocking, cookies and headers, resizing, caching, signed links, asynchronous webhooks, bulk capture, and PDF controls. The Free plan includes 1,000 shots per month without a card; paid plans start at $5 for 3,000 shots. Sign up free.
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Is a Featured Image required for every post?
No. A post can be published without one, but the theme may show an empty space or use another fallback, and social metadata may lack a preferred image.
Can I use the same image for multiple posts?
Yes. Select the existing Media Library item each time. Each post stores its own Featured Image assignment.
Why does changing Media settings not fix old thumbnails?
WordPress does not automatically recreate derivatives for existing uploads. Regenerate those sizes from the original files after changing registered dimensions.
Frequently Asked Questions
Can a page and a post use different thumbnail sizes?
Yes. Their templates can request different registered image sizes, even when both use the same Featured Image.
Will setting a Featured Image force it into a social preview?
No. The sharing service reads emitted metadata, and an SEO or Open Graph plugin controls which image is supplied.
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