Quick wins for a faster PC:
Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →The default WordPress thumbnail is 150 × 150 pixels, cropped to a perfect square. WordPress lets you change the thumbnail width and height, and choose between proportional resizing and an exact-dimension crop under Settings > Media. A theme, plugin, or the Image block can display a different size or crop, so the file generated by WordPress is not always the same as the image shape you see on a page.
What is the default WordPress thumbnail size?
WordPress.org documents the default thumbnail as 150 × 150 pixels, with a square crop. This is a default setting, not a promise that every theme or plugin will use a 150-pixel square for every card, gallery, or featured image. The official Edit Media documentation describes the default as “150px x 150px” and cropped as a perfect square.
| WordPress size or behavior | What it controls |
|---|---|
| Thumbnail | Built-in small image size; default 150 × 150 pixels and square-cropped. |
| Medium and Large | Maximum dimensions for other built-in generated sizes. |
| Full Size | The original uploaded image dimensions, subject to the uploaded file and site processing. |
| Theme or plugin size | A separately registered image variant that can have its own dimensions and crop rules. |
| Image block display | How a selected image is presented in the editor, including width, height, aspect ratio, and scale. |
The Settings Media screen documentation explains that these values set maximum dimensions for generated sizes. Therefore, a proportional thumbnail can be smaller than one or both values when the source image has a different aspect ratio.
How to change the thumbnail size in WordPress
- Sign in to WordPress. Use an account with permission to change media settings.
- Open Settings > Media. This is the administrative screen for the built-in Thumbnail, Medium, and Large dimensions.
- Find Thumbnail size. You will see separate Width and Height fields.
- Enter the maximum dimensions. For example, entering 200 for both fields defines a 200 × 200 target for a square thumbnail.
- Choose the crop behavior. Enable Crop thumbnail to exact dimensions when every generated thumbnail must use the specified width and height. Leave it disabled when WordPress should preserve the source proportions within those maximums.
- Save Changes. WordPress uses the saved values when creating the built-in image sizes.
Exact cropping gives you a predictable shape for grids and cards, but it removes part of an image when the source ratio does not match the target. Proportional resizing preserves the entire image, while the resulting width or height may be less than the value entered.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problems#1 Best Overall
- Used Book in Good Condition
Choosing dimensions for common layouts
| Layout goal | Typical setting approach | Trade-off |
|---|---|---|
| Uniform square cards | Set equal width and height and enable exact cropping. | Consistent boxes, but edges of some images are cut off. |
| Show the whole image | Use proportional resizing with maximum width and height. | No hard crop, but thumbnails may have different displayed shapes. |
| Wide article cards | Use a theme-registered wide size or a deliberate block aspect ratio. | The theme may not use the built-in Thumbnail setting. |
Why does my thumbnail look different from 150 × 150?
The theme may use another generated size
The built-in Thumbnail value does not control every image variant. Themes and plugins can register named sizes for featured images, archive cards, sliders, or galleries. The developer reference for add_image_size() documents proportional resizing, hard cropping, and crop-position options. It also identifies thumb and thumbnail as aliases for the reserved thumbnail name.
If changing Settings > Media has no visible effect on a particular card, inspect the theme’s image-size documentation or its template configuration. That component may request a custom size rather than the built-in thumbnail.
The Image block can crop the display without changing the file
The block editor has display controls separate from generated file dimensions. The Image block documentation describes resolution choices, width and height, aspect ratio, and Scale. Selecting an aspect ratio can make the image appear cropped in the editor or on the page. The Cover behavior fills the display area by cropping parts of the image as needed; it does not edit the original uploaded file.
This distinction explains many apparent conflicts: Settings > Media controls a generated image variant, while the block’s aspect ratio or Cover presentation controls what visitors see in that location.
The selected resolution may vary
In the classic editor, the available resolution choices are Thumbnail, Medium, Large, and Full Size, as described in Inserting images into posts and pages. In the block editor, available choices can depend on theme support and the dimensions of the uploaded image. A missing option does not necessarily mean that the thumbnail setting is wrong.
Generated size versus displayed size
Use these questions to identify which control you need:
- Are you changing the dimensions of a file WordPress generates? Use Settings > Media or a registered size.
- Are you changing the shape of an image inside a post or page? Check the Image block’s aspect ratio, Scale, width, height, or Cover settings.
- Does only one theme component look different? Check whether that component requests a custom size.
- Does the editor offer different resolution choices? Availability depends on the theme and source image as well as the standard sizes.
WordPress’s Image size and quality documentation also distinguishes pixel dimensions from file size and layout. Increasing pixel dimensions can make an image suitable for a larger display, but it does not by itself force a theme to use that variant.
Custom thumbnail sizes for themes and plugins
When a site needs a specific card shape, a developer can register a named size instead of relying on the built-in Thumbnail value. The documented function supports a width, height, hard-crop choice, and crop position. A proportional registration uses the dimensions as maximums; a hard crop produces the requested dimensions and can position the crop toward a chosen area.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Rank #3
Conceptual example
A news grid might register a 320 × 180 size with a hard crop so every card is 16:9. A portrait catalog might register 400 × 600 with a top-centered crop to keep faces or product tops visible. The exact implementation belongs in the theme or plugin code and should follow that project’s deployment practices.
Because custom sizes are independent variants, changing the built-in Thumbnail fields will not necessarily change those cards. The Page/Post Settings sidebar documentation notes that featured-image or post-thumbnail behavior varies by theme.
Troubleshooting thumbnail size problems
My thumbnails are not square
First check whether Crop thumbnail to exact dimensions is enabled under Settings > Media. If it is disabled, WordPress preserves proportions. If it is enabled but the front end is still not square, the theme may be using a custom size or CSS may be setting a different display ratio. The Image block’s aspect-ratio or Cover setting can also create a visual crop that is unrelated to the generated thumbnail.
The image is blurry after I increase the size
A larger target cannot create detail that was absent from the uploaded file. Check the original upload dimensions and whether the page is using a smaller generated variant. The editor’s resolution choice can affect which file is inserted, and available choices depend on the source image and theme.
Windows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallOutdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchImportant content is cut off
Exact cropping removes pixels to reach the requested shape. Use proportional resizing when the entire image must remain visible, or use a custom hard-crop position that keeps the subject in frame. For an Image block, test a different aspect ratio or Scale setting instead of changing the generated file.
Changing Settings > Media did not change a card
That card may request a theme- or plugin-registered size. Check the theme’s image-size configuration and the template that outputs the card. Also verify whether the editor is displaying a custom resolution or a Cover crop rather than the built-in Thumbnail.
The editor does not show the size I expect
The classic editor and block editor expose different controls. The block editor’s resolution list can vary with theme support and the uploaded image’s dimensions. Select the image and inspect its Resolution, Width, Height, Aspect ratio, and Scale controls before changing global media settings.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Performance and maintenance considerations
Every generated image variant consumes storage and may require processing when media is handled. Choose dimensions that match the actual layouts rather than creating unnecessarily large files for small cards. WordPress documentation covers the relationship among pixel dimensions, layout, and file size in Image size and quality.
- Use a smaller generated size for small cards instead of placing the Full Size original in every slot.
- Keep the crop shape consistent with the component so browsers do not display unexpectedly large images and then shrink them with CSS.
- Check the front-end template when a setting appears ineffective; the template may request another registered size.
- Remember that a display crop in the block editor changes presentation, not the original file.
Or skip the browser setup
If your goal is to capture a WordPress page, post, or thumbnail grid as an image or PDF rather than configure WordPress media sizes, ScreenshotNeo provides a one-request website screenshot API and MCP server. 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, CAPTCHAs, blank pages, timeouts, failed loads, and cache hits are not billed, and responses identify the result with X-Page-Verdict and X-Billed headers. Its MCP tools—take_screenshot, get_page_info, and capture_pdf—work with Claude, Cursor, and other MCP clients.
See the ScreenshotNeo documentation for all options, including full-page capture, CSS-selector element capture, device presets, retina scale, dark mode, custom CSS and JavaScript, waits, blocked resources, cookies, headers, geolocation, transparent backgrounds, resizing, caching, signed links, asynchronous jobs, bulk capture, and PDF settings.
cURL
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}`);The Free plan includes 1,000 screenshots per month with no card. Paid plans start at $5 for 3,000 screenshots, and every feature is available on every plan. Create a free ScreenshotNeo account.
WordPress thumbnail FAQ
Is 150 × 150 mandatory?
No. It is the documented default. Administrators can change the values, and themes or plugins can register other sizes.
Does cropping delete my original upload?
The Image block’s Cover and aspect-ratio controls do not edit the original file. Generated thumbnail variants are separate image outputs.
Should I use exact cropping or proportional resizing?
Use exact cropping for a fixed shape and proportional resizing when preserving the entire image matters more than uniform dimensions.
Why can two WordPress sites show different thumbnail sizes?
The built-in setting may differ, and each site’s theme or plugins may register and request different image sizes.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
Recommended Free Tools
