The short version: ShortPixel currently delivers the strongest overall compression with local WebP and AVIF generation, making it the safest general default. Imagify, from the team behind WP Rocket, is the simplest to set up and a particularly strong pick for photographers who need free AVIF support. Smush remains the most-installed option and a reasonable free default, especially if you're already in the broader WPMU DEV plugin ecosystem. EWWW Image Optimizer is the one to reach for if you specifically want unlimited compression processed on your own server with no monthly cap. This post sorts by what's actually constraining your choice, since for this category, that's rarely just "which compresses the most."
Quick picks by use case
| If your priority is... | Best pick | Free tier |
|---|---|---|
| The strongest overall compression, general default | ShortPixel | 100 images/month free |
| Simplicity, plus free AVIF support | Imagify | ~20MB/month (roughly 200 images) |
| Most widely used, easy default choice | Smush | Unlimited, but lossless compression only |
| Unlimited free compression processed on your own server | EWWW Image Optimizer | Unlimited local compression, no monthly cap |
| An image-heavy or high-traffic site (portfolios, WooCommerce) | Optimole | Free tier available; paid tiers add real-time CDN delivery |
Local processing versus cloud processing: the distinction that actually matters most
Before comparing individual plugins, it's worth understanding the more fundamental choice underneath all of them: local optimization processes images directly on your own hosting server, while cloud optimization sends your images to the plugin vendor's servers to be compressed there, then returns the optimized file. Local processing (EWWW's core plugin, Smush's free tier) keeps everything private and avoids any monthly image cap, but uses your own host's CPU resources to do the compression work. Cloud processing (ShortPixel, Imagify, Optimole) spares your host's resources entirely and typically adds WebP/AVIF conversion and sometimes a CDN, but usually comes with a monthly image allowance or credit-based pricing once you're past a free tier.
This distinction also matters practically on restricted shared hosting: some budget hosting environments disable the server functions EWWW's local processing depends on, in which case it silently falls back to using its own cloud API anyway, which defeats the specific reason you might have chosen it. If server resource control matters to your decision, it's worth confirming your host actually supports local processing before assuming EWWW will behave as expected.
ShortPixel: the strongest general-purpose default
Independent compression testing consistently places ShortPixel among the top performers for overall file size reduction, and it supports both WebP and AVIF generated locally as ordinary image files your host can serve directly, rather than depending on the vendor's own CDN to deliver the modern format. Its pricing model, monthly subscriptions or one-time credit packs, is specifically well suited to a site that publishes in bursts rather than a steady daily trickle, since unused credits from a one-time pack don't expire the way a monthly allowance would. For a larger media library, several thousand images and beyond, ShortPixel's per-image-size reporting and straightforward restore option are specifically noted as becoming more valuable at that scale than a competitor's more basic dashboard.
Imagify: the simplest setup, and the strongest free AVIF option
Imagify, built by the same team behind WP Rocket, is consistently described as the most straightforward of these tools to configure, and in independent PageSpeed testing it tied for the top desktop performance score among competitors tested. It's specifically recommended for photographers needing genuine AVIF support with per-image control, and unlike some competitors, Imagify includes AVIF generation in its free tier rather than reserving it for a paid plan. Its free tier does impose a maximum image size limit, which caused it to fail compressing some very large test images in independent testing, worth knowing if your site regularly handles unusually large source files.
Smush: the safe, most widely used default
Smush holds the largest install base of any WordPress image optimization plugin, over a million active installs with a strong average rating, and its free tier covers real, useful ground: compression on upload, automatic resizing of oversized uploads, lazy loading, and bulk optimization of your existing media library. Its free compression is limited to a more conservative lossless mode rather than the more aggressive lossy compression some competitors offer for free, meaning file size reductions tend to be more modest. Its clearest specific advantage is for anyone already paying for the broader WPMU DEV plugin suite, since Smush Pro is bundled in at no additional cost, making it close to free for existing customers of that ecosystem, even though it wouldn't be the strongest standalone pick on compression alone.
EWWW Image Optimizer: unlimited free compression, with no monthly counting
EWWW's defining feature is unlimited free local compression, an actual, uncapped free tier rather than a limited monthly allowance, which makes it a genuinely strong choice for a large media library on a host with adequate CPU headroom to handle the processing itself. It's also the only plugin in this comparison that includes SVG and PDF file optimization as a standard feature, worth knowing if your site handles either file type regularly. Cloud-based paid tiers are available starting at a modest monthly cost for sites that want WebP/AVIF conversion without relying on local server processing.
Optimole: for sites where images are the whole point
If your site is genuinely image-heavy, a photography portfolio, a visually driven WooCommerce store, or anything with large, frequently updated galleries, Optimole's real-time CDN-based delivery approach is built specifically for that scenario, handling resizing, format conversion, and delivery through its content delivery network as one integrated service rather than a separate compression step you manage yourself. It trades some of the granular per-image control other tools offer for a more hands-off, end-to-end approach specifically suited to a high volume of images.
What this doesn't mean: the honest nuance
Compression alone doesn't fix the more fundamental image-weight problem covered in the earlier post on diagnosing a slow WordPress site: uploading a 4,000-pixel-wide photo to display in an 800-pixel-wide space wastes bandwidth regardless of how well it's compressed afterward. These plugins are a genuinely important layer, but they work best paired with actually uploading appropriately sized images in the first place, not as a substitute for that basic discipline.
It's also worth repeating a rule that applies here just as it does to caching and security plugins covered earlier in this series: don't run two image optimization plugins simultaneously, particularly if both are configured to handle WebP conversion or lazy loading. Both will attempt to process the same images, causing conflicts rather than combined benefit. Pick one, based on the priorities in this post, and use it exclusively.
Frequently asked questions
Is a free tier actually enough for a small site, or will I need to pay eventually?
For a small site that adds a modest number of new images each month, free tiers from ShortPixel, Imagify, or Smush's unlimited-but-lossless tier are often genuinely sufficient long-term. You're most likely to outgrow a monthly-allowance free tier specifically if you regularly bulk-upload large batches of new photos, at which point either a paid cloud tier or switching to EWWW's uncapped local processing becomes worth considering.
Is local processing actually safer for privacy than sending images to a cloud service?
If your images contain sensitive or confidential content you specifically don't want leaving your own server, local processing (EWWW's core plugin, or Smush's free tier) avoids that concern entirely, since compression happens on your own hosting rather than a third party's servers. For most public-facing website images, this isn't a meaningful practical concern, but it's a legitimate reason to prefer local processing if it applies to your specific situation.
Do I still need a separate image CDN if I already have a compression plugin?
Not necessarily, and for most small to medium sites, a good compression plugin alone (paired with your existing caching setup, covered in the earlier post on caching plugins) is sufficient. A dedicated image CDN becomes more clearly worth adding specifically for high-traffic, globally distributed audiences, or image-heavy sites where Optimole's integrated approach, covered above, is often the simpler path to the same benefit.
Will optimizing my images actually make them look noticeably worse?
Done properly, no. Modern lossy compression (available in ShortPixel, Imagify, and most competitors' paid or higher-quality settings) is specifically designed to reduce file size in ways imperceptible to most viewers at normal viewing distances and screen sizes. If you're specifically concerned about visible quality loss, lossless compression modes (Smush's free tier, or a lossless setting available in most competitors) preserve visual quality entirely, at the cost of a smaller file size reduction.
Compressed images help your visitors, but none of it matters if the server delivering them is slow or unreliable to begin with. The next post steps back to that foundation: the strongest WordPress hosting providers available right now, sorted by the kind of site you're actually running.
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