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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsThere is no single featured-image size that every WordPress site should use. The active theme, template and display slot determine the rendered dimensions and crop. Start with the theme’s featured-image guidance, identify the largest slot your image must fill, and upload a source large enough for that slot. If Google Discover is a goal, use a separate target: at least 1,200 pixels wide, more than 300,000 total pixels and a 16:9 composition.
What WordPress actually requires
WordPress calls a featured image a post thumbnail: an image representing a post, page or custom post type. WordPress itself does not impose one universal canvas. A theme must declare featured-image support and decides which generated size, aspect ratio and template markup to use. See the WordPress Theme Handbook for how themes register and display featured images.
That means a 1,200 × 675 image can work well on one site but crop badly on another. A theme may show the same upload in a post header, an archive card, a related-post grid and a mobile layout, each with different proportions. Treat the upload as source material for those slots, not as a guarantee of the final display.
WordPress’s built-in image sizes
When an image is uploaded, WordPress can generate several derivative sizes. These are administrator settings and theme options, not universal featured-image recommendations.
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| Generated size | Default limit | What the limit means |
|---|---|---|
| Thumbnail | 150 × 150 px maximum | Usually a square derivative; themes can crop it. |
| Medium | 300 × 300 px maximum | WordPress scales within the maximum dimensions. |
| Medium Large | 768 px wide, no height limit | Width is constrained while proportional height is retained. |
| Large | 1,024 × 1,024 px maximum | Scaled proportionally within the maximum box. |
| Full | Original uploaded resolution | The original file, subject to site and server limits. |
Administrators can change defaults under Settings → Media, and theme developers can register custom sizes. A theme’s custom size may be the one actually used for a featured image.
How themes scale and crop featured images
Scaling preserves proportions
With cropping disabled, WordPress scales an image proportionally to fit the requested dimensions. The result remains the same shape as the source, although it may be smaller than either requested maximum.
Hard crops change the composition
With cropping enabled, WordPress cuts the image to the registered width and height. The default crop position is centered, but a theme or developer can specify another position. Faces, logos and text near an edge can disappear. The set_post_thumbnail_size() reference documents these settings.
Changing a size does not repair old files
If you change a registered dimension or crop setting, WordPress does not automatically recreate every previously generated derivative. Existing uploads may need thumbnail regeneration. Check the rendered result after any theme change rather than assuming old images have adopted the new dimensions.
Block themes add visual controls
The Post Featured Image block exposes dimension and aspect-ratio controls. Which ratios are available can depend on the theme. The block documentation explains those controls. A block setting can alter the presentation even when the original upload is unchanged.
A practical way to choose the source dimensions
- Check the active theme. Read its featured-image documentation, inspect the Site Editor or template files, and note registered image sizes.
- List every important slot. Include the single-post header, homepage hero, category/archive cards, related posts, social previews and mobile layouts.
- Find the largest rendered width. Use the browser’s responsive developer tools or the theme’s layout settings. Distinguish CSS display width from the file’s pixel dimensions.
- Determine the shape and crop. Record each slot’s aspect ratio and whether it uses proportional scaling, a hard crop or a focal-position setting.
- Prepare a safe composition. Keep faces, logos and essential words toward the center or well inside the crop-safe area. Avoid placing critical detail against the extreme edges.
- Export a source for the largest slot. Do not upload a tiny image and expect WordPress to create detail that was never present. Conversely, an oversized original increases storage and download cost.
- Preview real templates. Check a post header, archive card and narrow viewport. Confirm that the selected WordPress derivative is sharp and that no important content is cut.
- Regenerate derivatives after structural changes. If dimensions or crop rules changed, recreate old sizes and review representative older posts.
There is no magic number that replaces this process. A source around 1,200–1,600 pixels wide is often practical for broad editorial layouts, but the correct value is the largest actual display slot on your site, not a generic internet rule.
When Google Discover is the target
Google Discover has its own recommendation, separate from WordPress. Google says images should be at least 1,200 pixels wide, contain more than 300,000 total pixels and use a 16:9 aspect ratio. Its example is 1,280 × 720 (921,600 pixels). Read Get on Discover for the current guidance.
For a 16:9 source, 1,200 × 675 is the minimum-width equivalent and 1,280 × 720 gives additional margin. These values are Discover targets, not WordPress requirements; a theme may still crop the image into a different card ratio.
Enable large previews
Google advises allowing large image previews with max-image-preview:large or by using AMP. Supply a representative image through structured data or the og:image metadata used for sharing. These signals improve the chance that Google can identify the intended image, but they do not force a particular preview.
Design for automated cropping
Google states that “Google’s selection of an image preview is completely automated and takes into account a number of different sources to select which image is shown on Google.” Keep the main subject in a landscape-safe central area, avoid extreme aspect ratios and do not use a generic logo as the preferred image. A valid metadata reference cannot guarantee the exact image or crop shown.
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Dimensions, display size and file weight are different
- Pixel dimensions are the width and height encoded in the file.
- Rendered dimensions are the CSS size at a particular viewport.
- Aspect ratio is the relationship between width and height.
- File weight is the compressed download size.
An image wider than the content area can waste bandwidth and may disrupt a layout; an image smaller than a high-density display can look soft. WordPress’s image size and quality guidance recommends balancing clarity with file size. Google’s image guidance likewise favors speed and quality together. Do not increase resolution or switch formats indiscriminately: inspect the actual visual result and loading weight.
Use responsive output where your theme supports it. WordPress can emit srcset and sizes candidates so a browser selects an appropriate file. Google also describes responsive images and the <picture> element with an img fallback in its Image SEO Best Practices.
Preview every template before publishing
Open a draft at desktop and narrow breakpoints. Check the focal subject, headline readability, contrast, lazy-loaded areas and card grids. A full-width hero can be crisp while the same image’s square archive derivative cuts off the subject. If your theme offers a focal-point picker, set it deliberately; otherwise, recompose the source with generous margins.
For a repeatable visual check, capture the public post and archive pages at the viewport sizes your readers use. ScreenshotNeo can render those pages so you can compare desktop and mobile crops without manually repeating browser steps.
Or skip the browser setup
ScreenshotNeo is a website screenshot API and MCP server. Send one GET request to capture a rendered WordPress page as PNG, JPEG, WebP or PDF, then inspect the result for crop and layout problems.
cURL (the API details are in the ScreenshotNeo docs):
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curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://example.com/sample-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/sample-post"}, timeout=90)
open("shot.webp", "wb").write(r.content)Node.js:
const q = new URLSearchParams({ access_key: 'YOUR_API_KEY', url: 'https://example.com/sample-post' });
const res = await fetch(`https://api.screenshotneo.com/v1/shot?${q}`);Before capture, ScreenshotNeo accepts cookie or consent banners 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 as clean shots, and response headers report the page verdict and billing status. Its MCP server provides take_screenshot, get_page_info and capture_pdf tools for Claude, Cursor and other MCP clients. You can use viewport and device presets, full-page capture, CSS selectors, waits, custom CSS or JavaScript and other options to test responsive crops.
There are 1,000 screenshots per month free with no card. Paid plans start at $5 for 3,000 shots; every feature is on every plan. Create a free ScreenshotNeo account to check your WordPress layouts.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Troubleshooting featured-image problems
The image is blurry
Identify the derivative selected in the HTML and compare its pixel width with the rendered width, especially on high-density screens. Upload a larger source or adjust the theme’s registered size, then regenerate old derivatives.
The subject is cut off
The slot is probably hard-cropped or uses a different ratio. Move the focal subject inward, change the focal position if the theme supports it, or prepare a composition that tolerates the crop.
The new dimensions affect only new posts
Changing a registration does not recreate existing files. Regenerate thumbnails and clear any page, CDN or image cache before judging the result.
Discover shows another image
Google’s preview selection is automated. Verify that the preferred image is representative, available to crawlers, present in structured data or og:image, and eligible for large previews; then allow time for recrawling. No setting guarantees a specific Discover crop.
The page is slow after uploading larger files
Use responsive candidates, compress at a quality appropriate to the image, and avoid serving the full original to every slot. Check file weight and visual quality together rather than solving softness by endlessly increasing resolution.
Quick decision checklist
- Theme documentation and templates checked.
- Largest rendered slot measured.
- Aspect ratio and crop behavior confirmed.
- Source is large enough without being needlessly enormous.
- Faces, logos and text have crop-safe margins.
- Desktop, mobile, header and archive views inspected.
- Old derivatives regenerated after size changes.
- For Discover: 1,200-pixel minimum width, over 300,000 pixels, 16:9, large-preview eligibility and representative metadata verified.
Frequently Asked Questions
Should every WordPress featured image be 1200 × 628 pixels?
No. That ratio is a common social convention, not a WordPress requirement. Use the active theme’s slot dimensions; use Google’s separate 1,200-pixel, over-300,000-pixel, 16:9 recommendation only when Discover is a target.
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No. Themes register different derivatives and crops. A reusable source can work, but its dimensions and composition should be validated against each theme’s largest slot.
Does WordPress automatically crop the original upload?
It generates derivatives according to registered settings. Whether a derivative is proportionally scaled or hard-cropped depends on the requested size and crop configuration.
How do I know which featured-image file a page uses?
Inspect the rendered image element and its srcset in your browser’s developer tools, then compare that candidate’s dimensions with the slot’s CSS size.
The Bottom Line
Choose the featured-image dimensions from your active theme’s largest real display slot, verify its crop behavior and preview every responsive layout. Treat Google Discover’s 1,200-pixel, 16:9 guidance as a separate platform target—not a universal WordPress rule.
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