ShortPixel vs Imagify vs Smush is often presented as a compression-quality contest, but the vendors do not publish one shared test that establishes a universal quality winner. A practical difference that can be compared directly is how each service meters the work: ShortPixel counts credits per file, Imagify counts megabytes of images per month, and Smush does not list a monthly image or megabyte allowance but moves several capabilities behind Pro. Start by matching that meter and feature boundary to your library, then test visual quality on your own representative images.
Three plugins, three different meters
ShortPixel Image Optimizer spends one credit per file whenever it achieves at least a 5 percent reduction, and nothing at all when it cannot. Derivatives are billed individually, so every thumbnail is its own line item, and each WebP or AVIF counterpart adds another. ShortPixel’s published illustration totals 18 credits for a single upload that produces eight thumbnails and a next-generation copy of all nine files. The free plan is 100 credits per month, and unlimited monthly credits are listed at $9.99 per month.
Imagify does not count files. It counts the weight of the images you send. The free Starter plan allows 20MB of images per month, which Imagify describes as roughly 200 images, with a 2MB maximum per uploaded image. Growth is $5.99 per month, or $4.99 per month billed yearly, for 500MB per month (about 5,000 images) with no upload size cap and $5 per additional gigabyte. Infinite is $11.99 per month, or $9.99 per month billed yearly, for unlimited images. Quota is shared across unlimited websites on one account, which matters if you run several sites.
Smush has no monthly image or megabyte allowance in either tier. Its free plan is limited by which files it will touch and how the results are delivered. Images over 5MB are skipped in the free version, while Smush Pro compresses files up to 256MB. Free Smush compresses resized versions by default; full-size image compression is a Pro feature. WebP and AVIF conversion with automatic serving, the image CDN, and automatic image resizing are also Pro.
What each free plan actually covers
The free tiers are not equivalent. ShortPixel’s 100 monthly credits are file events, so a WordPress install that generates eight thumbnails per upload and also produces WebP counterparts will spend that allowance on roughly five new photographs under ShortPixel’s published 18-credit example. A site that generates fewer derivatives will get a different result, so inspect the active image sizes before treating 100 credits as a monthly upload count.
Imagify’s 20MB is a weight budget. A site that uploads pre-resized 150KB images can put well over a hundred files through that allowance in a month; a site that uploads 1.8MB camera exports will exhaust it in about eleven images. The 2MB per-file ceiling on the free plan is the harder constraint for photographers, because oversized originals are rejected rather than merely counted.
Smush’s current WordPress.org listing does not present a monthly image or megabyte quota. That removes the monthly allowance calculation, but the free tier still compresses resized versions rather than full-size originals, skips files over 5MB, and does not provide automatic WebP or AVIF serving. It also includes lazy loading and Directory Smush for files stored outside the media library. For a large existing library, those feature boundaries matter more than a monthly counter.
Where each one breaks first
Each plugin has a predictable failure point, and it is worth knowing yours before installing anything.
- ShortPixel: thumbnail multiplication. Credit planning goes wrong when site owners count originals instead of derivatives. Exclude thumbnail sizes the live theme never requests before a bulk run, not after.
- Imagify: the weight budget. Because the meter is megabytes, an editorial habit of uploading straight from a camera can burn a paid quota that would comfortably cover a resized workflow. Resizing on upload, which Imagify can do to a maximum width of up to 2560 pixels, changes the cost more than the compression setting does.
- Smush: the delivery gap. Converting to WebP or AVIF and serving those files automatically is a Pro feature, so a free Smush site can pass a compression audit and still fail a “serve images in next-gen formats” recommendation.
How much control you get over compression
ShortPixel exposes three named modes — Lossy, Glossy, and Lossless — and expects you to choose. That is useful when different parts of a site have different tolerances, and it is extra work when they do not.
Imagify has moved in the opposite direction. Its default is Smart Compression, which balances quality and file size automatically with no setting to pick, and it keeps an optional lossless mode for quality-sensitive libraries. If you want to stop thinking about compression levels, that is the point.
Smush offers lossless and lossy compression without the intermediate tier, which fits its broader positioning as a plugin that works acceptably without configuration.
Next-gen formats: who converts and who serves
Conversion and delivery are separate problems, and this is where the three plugins diverge most in practice. ShortPixel converts to WebP and AVIF, can compress existing WebP files, and provides delivery options plus a global CDN that also covers CSS and JS. Imagify includes WebP and AVIF conversion in its free plan and falls back to the original format for browsers that do not support the newer one. Smush’s automatic next-gen serving is a Pro capability, and its CDN — advertised as 119 servers with up to 500GB of bandwidth — is Pro only.
In all three cases, generating a modern-format file is not the same as delivering it. Caches, CDNs, and server rewrite rules can leave browsers receiving the original JPEG regardless of which plugin produced the WebP. Verify the file type a browser actually downloads rather than the count on a plugin dashboard.
Backups and the ability to undo
All three keep a path back, but on different terms. ShortPixel stores originals in a backup folder when the backup option is enabled. Imagify moves originals to a dedicated backup folder as long as the Backup option stays active, which is its default. Smush does not delete originals; in the free tier it is compressing resized versions rather than replacing the full-size file. Confirm the restore path on a single test image before any bulk run, on whichever plugin you pick.
Which one fits which site
If your library is large and already resized, and you mainly want the compression to stop being a recurring chore, Smush free is the lowest-friction starting point — then the question becomes whether next-gen serving and the CDN are worth a Pro membership.
If you upload steadily and want predictable pricing without counting thumbnails, Imagify’s megabyte model is easier to forecast, and its unlimited tier removes the arithmetic entirely.
If you want explicit control over compression mode, PDF and HEIC handling, per-size exclusions, and a credit model that only charges when a file actually got meaningfully smaller, ShortPixel is the most configurable of the three. Its credit accounting is covered separately in our ShortPixel pricing guide.
What none of them do
No image optimizer guarantees a search ranking or a passing Core Web Vitals assessment. Compression reduces transferred bytes; server response time, caching, scripts, fonts, and theme behaviour remain separate problems. None of the three is a substitute for serving an appropriately sized image — compressing a 3,000-pixel file into a 600-pixel column is still waste. And only one of them should own a given media library at a time. When two optimizers claim the same files, you get inconsistent skip states and restore folders that disagree with the images your visitors actually receive.
Verification note
Plan names, prices, quotas, and free-tier limits in this comparison were read from the vendors’ own published material on 12 September 2026: ShortPixel’s WordPress.org listing and knowledge base, Imagify’s pricing page, and the Smush plugin listing. At that date the current releases were ShortPixel Image Optimizer 6.5.6, Imagify 2.3.4, and Smush 4.3.2. All three vendors change plans and limits without notice, so confirm the live figures before a purchase decision.