Ask five professionals which format to use for Email Marketing and you'll get five confident, conflicting answers. The data is less ambiguous: each format buys a specific trade-off, and Email Marketing rewards some trade-offs much more than others.
Formats worth considering
| Format | Compression | Transparency | Animation | Support (2026) |
|---|---|---|---|---|
| WebP | Lossy and lossless | Yes | Yes | over 96% of browsers in use in 2026 (caniuse) |
| AVIF | Lossy and lossless | Yes | Yes | over 93% of browsers in 2026, including Chrome, Firefox, Safari and Edge |
| JPEG | Lossy | No | No | every browser and device made in the last 25 years |
| PNG | Lossless | Yes | No | every browser since the early 2000s |
| SVG | Vector | Yes | Yes | all modern browsers |
Five formats cover effectively every Email Marketing scenario. What separates them is below.
WebP: the default in 2026
25-34% smaller than an equivalent JPEG, per Google's published study, with support across over 96% of browsers in use in 2026 (caniuse). For most Email Marketing work that combination — smaller files, near-universal support, transparency and animation included — makes WebP the sensible starting point. The WebP converter turns existing JPEG/PNG libraries into WebP in batches.
AVIF for the heavy lifting
AVIF goes further: roughly half the size of a comparable JPEG, and about 20% under WebP. Encoding is slower and very old browsers miss it (over 93% of browsers in 2026, including Chrome, Firefox, Safari and Edge), so the classic pattern is AVIF first with a fallback. Try one hero image through the AVIF converter and compare.
Where the classics still win
JPEG remains the file that opens absolutely everywhere — email clients, ancient CMS installs, kiosk software. PNG keeps its role wherever Email Marketing needs sharp edges, text or transparency: a 1080p screenshot is typically 150-400 KB; a 12-megapixel photo can exceed 15 MB.
Don't rasterize your logos
Logos, icons and diagrams belong in SVG: icons usually weigh 1-10 KB, less than a single photo thumbnail, and they stay crisp at any resolution. Exporting a logo as a 2,000-pixel PNG when an 8 KB SVG exists is the most common self-inflicted wound in Email Marketing.
A working strategy for Email Marketing
Photographs go modern (WebP or AVIF) with a JPEG fallback where compatibility is unknown. Graphics and UI go PNG or SVG. Everything gets resized to its real display dimensions before upload — serving a 4000-pixel image in an 800-pixel slot is pure waste — and below-the-fold images get loading="lazy".
The quality dial matters more than the tool: JPEG at 80-85% is visually identical to 100% for most photos and roughly half the size.
Image SEO beyond the format
Filenames describe the subject in plain words with hyphens — search engines read them, and so do you in six months. Alt text describes the image for screen readers and image search in one natural sentence, not a keyword pile.
Dimensions in the HTML (width and height attributes) stop layout shift, the CLS half of Core Web Vitals. Large previews need one meta line — max-image-preview:large — for Google Discover to show your images at full size.
None of these depend on the format, and all of them compound with it: a light, well-described, properly-sized image is the complete package for Email Marketing.
The metadata question nobody asks
Every photo from a camera or phone carries hidden baggage: capture date, device model, exposure settings and — on phones — often GPS coordinates. Conversion is one of the moments where that baggage can be kept or dropped.
For files headed to the public web, dropped metadata is a privacy feature: nobody needs your home coordinates embedded in a product photo.
The practical rule: treat the original as the metadata archive and the converted copy as the public version. That division of labour answers most privacy and copyright questions before they come up.
The Core Web Vitals angle
Images are usually the heaviest asset class on a page, so format choice flows straight into Largest Contentful Paint — the Core Web Vitals metric Google weighs for ranking. Lighter images, earlier paint, better scores: the chain is that direct.
Pair the format change with loading="lazy" on below-the-fold images and correct display dimensions, and the speed gain typically doubles.
Measure before and after with PageSpeed Insights — the image-weight line item makes the improvement concrete instead of theoretical.
Where the rules bend per platform
WordPress converts uploads to WebP on modern versions but keeps the original — uploading lighter files still pays. Shopify and most e-commerce platforms recompress aggressively; feed them the highest-quality source and let the CDN do the dirty work.
Social platforms recompress everything on upload, so chasing the perfect encode for them is wasted effort — correct dimensions matter far more there.
Measuring the result
Run the page through PageSpeed Insights before touching anything and note two numbers: total image weight and Largest Contentful Paint. Those are your baseline.
Convert the images, redeploy, run the same test. Lighthouse in Chrome DevTools gives the same data offline if you prefer testing before going live.
If the numbers barely move, your bottleneck is elsewhere — scripts or server response — and you just saved yourself from optimizing the wrong thing.
Email Marketing: quick decisions
Photos and hero images: WebP, or AVIF where you control the stack. Logos, icons, diagrams: SVG, with PNG as the raster fallback. Screenshots and UI captures: PNG.
Email attachments and downloads: JPEG, because it opens on whatever the recipient has. Short animations: animated WebP over GIF — same clip, a fraction of the megabytes. Print handoffs: TIFF or high-resolution PNG, never a web-compressed file.
Tape this list next to the upload button: every Email Marketing decision above repeats weekly, and deciding once beats re-debating it per file.
Common mistakes in Email Marketing
Serving originals. Uploading camera files straight from the device puts multi-megabyte images behind every thumbnail. Resize to display dimensions first; the format choice comes second.
One format for everything. Photos, screenshots and logos compress on different curves — forcing them all into one format guarantees at least one of them is badly served.
Never measuring. PageSpeed Insights and Lighthouse both show exactly how many kilobytes your images cost. Run the test once before and once after converting, and the improvement stops being theoretical.
A bandwidth sketch, in real numbers
Sketch a typical Email Marketing page: 25 images averaging 350 KB as JPEG is 8.75 MB of pictures. The same set as WebP, at a conservative 30% saving, drops to about 6.1 MB; as AVIF, near 4.4 MB.
Multiply by traffic and the sketch becomes a bill: at 10,000 page views a month, the WebP move alone spares roughly 26 GB of transfer — bandwidth your host does not invoice and your visitors do not wait for.
The exact percentages vary with content, which is why the one-page test beats any projection — but the direction never flips.
Make the decision once, for everyone
Solo habits break the day a second person uploads. A one-paragraph internal rule — which formats for which asset types, maximum dimensions, where masters live — outperforms any amount of after-the-fact cleanup.
Review it twice a year against browser-support data; the 2026 answer (WebP-first) will eventually rotate, and the rule should rotate with it.
The short version
WebP first, AVIF where you control the stack, JPEG as the universal envelope, PNG and SVG for graphics. Resize to display dimensions before anything else. Measure once before and once after — the delta is the whole argument.
Shipping this without breaking things
Week one: audit. Pull the ten heaviest pages from analytics, note their image weight, and convert only those assets. High-traffic pages pay back first and surface problems fastest.
Week two: templates. Point new uploads at the chosen formats — the WebP converter handles the backlog in batches — and add width and height attributes wherever they are missing.
Keep a one-line changelog of what was converted when — six months later that note answers every "why does this page look different" ticket in seconds.
What the CDN adds on top
Formats decide the floor; delivery decides the rest. A CDN with automatic format negotiation serves AVIF or WebP to capable browsers and JPEG to the stragglers — from a single uploaded master.
Responsive markup does the same for dimensions: srcset and sizes let the browser pick the smallest adequate file, so a phone never downloads a desktop hero image.
Stack the three layers — right format, right dimensions, right delivery — and each multiplies the others; that is where the dramatic before/after screenshots come from.
The format guides behind this ranking
Every recommendation above unpacks further: our WebP format guide, our AVIF format guide and our PNG format guide cover the three workhorses in depth.
For the hands-on path, the JPEG to WebP guide walks the exact conversion most Email Marketing libraries start with.
Accessibility: the other half of image work
Alt text is the cheapest professional upgrade in Email Marketing: one natural sentence describing what the image shows and why it is there. Screen readers speak it, image search indexes it, and broken-image states display it.
Decorative images — dividers, ambient backgrounds — take an empty alt attribute instead, which tells assistive tech to skip them. Describing decoration is as unhelpful as ignoring content.
Text baked into images deserves suspicion: it cannot be read aloud, translated, searched or resized, and it blurs on the wrong screen density. If the words matter, put them in HTML next to the image, not inside its pixels.
Accessibility and SEO reward the same habits here, so the effort pays twice on every single asset.
Contrast check last: text or icons over photos need a tested overlay or scrim, because a hero that is legible on your monitor can vanish on a dim phone in sunlight.
One anti-pattern to retire: pasting the filename or a keyword list into the alt attribute. Assistive tech reads it aloud verbatim, and search engines discount it — a plain descriptive sentence beats both habits with less effort.
Quick Answers
What single format should I pick for Email Marketing if I must choose one?
WebP. It compresses 25-34% under JPEG, supports transparency, and reaches over 96% of browsers in use in 2026 (caniuse) — the rare case where the convenient answer and the technically correct one match.
Is JPEG obsolete in 2026?
No — it is the universal fallback. Anything that must open in unknown environments (email attachments, downloads, legacy systems) still travels safest as JPEG, even when your primary delivery is WebP or AVIF.
How much speed do modern formats actually buy?
On image-heavy pages, converting a JPEG library to WebP typically trims a quarter to a third of image weight; AVIF roughly halves it. Since images dominate page size, that translates directly into faster loads and better Core Web Vitals.
Should logos be PNG or SVG?
SVG whenever the logo exists as vector art — a few kilobytes, infinitely sharp. PNG is the fallback for raster-only logos or platforms that reject SVG uploads.
Do I need different formats for retina screens?
Not different formats — different sizes. Serve 2× dimensions for high-density screens via srcset, and let the format (ideally WebP/AVIF) keep the bytes in check.
Does Google rank pages by image format?
Not directly — Google ranks the outcome. Image weight drives Largest Contentful Paint, and Core Web Vitals feed rankings, so a lighter format improves SEO through speed rather than through the file extension itself.
Are GIFs still acceptable for Email Marketing?
Only out of habit. GIF caps at 256 colors and balloons in size: a 5-second animation easily reaches 5-10 MB; the same clip as animated WebP is a fraction of that Animated WebP delivers the same clip dramatically lighter, and every current browser plays it.
How many formats should one Email Marketing project use?
Usually three: a modern format for delivery, a universal fallback, and SVG for vector assets. More than that and the upload rules stop being memorable, which is when mistakes creep back in.
Is it worth re-converting an old image library?
Run the arithmetic on one folder first: convert a sample, multiply the saving by the library size. Libraries behind high-traffic pages almost always justify it; archives nobody serves can stay as they are.
Do stock photos need converting before upload?
Often yes — stock sites deliver maximum-quality JPEGs sized for print, not for pages. Resize to display dimensions and convert to your delivery format, and a 12 MB download becomes a 200 KB asset.
Mini glossary
Alpha channel. The per-pixel transparency layer. Formats without one flatten transparent areas, usually onto white.
Lossy / lossless. Whether compression discards data permanently or packs it reversibly. The single most consequential word on any format's spec sheet.
Bit depth. How many shades each color channel can hold; higher depth means smoother gradients and bigger files.
Encoding. The act of writing pixels into a format's structure. Slow encoders (AVIF) trade time for smaller output.
Artifacts. Visible compression damage — blockiness, halos around edges — produced by aggressive lossy settings or repeated re-saves.
Color profile. Metadata describing which exact colors the numbers mean. Mismatched profiles are behind most "the colors changed" complaints.
Container. A file wrapper that can hold image data plus extras — depth maps, multiple frames — as HEIC does.
Rasterize. Converting vector shapes into fixed pixels; the one-way step that costs a logo its infinite sharpness.
The audit that pays for itself: take the three heaviest images in your current Email Marketing project, run them through the converter, and total the savings. That number is your business case.
Written by Giovanni Picaro, a web developer who has been building image tools and optimizing sites since 2019. Sources: MDN image format reference and Google web.dev. Last reviewed: 2026.