PNG vs WebP vs AVIF: Which Image Format Should You Use?
Practical decision guide for the three modern web image formats: what each actually trades off, which platforms still reject which, and how to pick without second-guessing.
Prerequisites
- An image you want to convert or optimize
- Omnvert image converters
- A browser to visually verify the output
Step-by-step
- 1
Understand what each format actually trades off
PNG is lossless, produces large files, and is the right choice for logos, UI assets, and screenshots with text — anywhere pixel-perfect edges and full alpha matter. Never use PNG for web photos; it will bloat every page. WebP, Google's format, is lossy or lossless, typically 25–35% smaller than JPEG at the same quality, and is supported in every modern browser since 2020 — but still rejected by some older CMSes and most email clients. AVIF is AV1-based, roughly 50% smaller than JPEG for photos, supports HDR and wide color, but encodes much more slowly and still trips up older enterprise tools and a few desktop apps.
- 2
Pick format by use case
Logo or icon with transparency → PNG (or WebP if size matters and your CMS accepts it). Product photo on e‑commerce → WebP with a JPEG fallback for old browsers. Hero image on a modern site → AVIF with a WebP fallback. Screenshot with text → PNG; AVIF and WebP at lower quality settings introduce blur on sharp text edges. Email attachment → JPEG, because most email clients still choke on WebP and AVIF. Social media upload → JPEG or PNG; platforms re‑compress anyway, so there's no point handing them an AVIF they'll re‑encode to JPEG on the other side.
- 3
Test transparency support before committing
WebP supports alpha, but older Windows tools — older Paint, some Office versions — still can't open WebP at all, let alone display alpha correctly. AVIF alpha is supported in spec but tooling is spotty; some image editors flatten it on open. PNG stays the safest bet for transparency if the file will ever be opened outside a browser — by a designer, a print shop, a stakeholder's old Office install.
- 4
Know when lossless WebP is worth it
Lossless WebP is smaller than PNG for photos but larger for graphics. Use lossy WebP for photos — quality 80–85 is typically indistinguishable from the source — and lossless WebP only when you need transparency plus a smaller size than PNG, for example on an illustration or a UI asset with a transparent background where you've already measured the PNG is too heavy.
- 5
Check CMS and platform support before a bulk conversion
WordPress supports WebP natively since 5.8; Shopify serves WebP automatically; Squarespace converts on upload; Figma imports WebP and exports PNG/JPEG/SVG/WebP; Notion renders WebP inline. The laggards: Gmail and Outlook accept only JPEG and PNG in the composer, some enterprise DAMs still reject WebP uploads, and many legal/government portals list acceptable formats and won't budge. Confirm the target accepts the format before you rewrite your whole image pipeline.
- 6
Convert and validate the output size
Use the Omnvert converters and compare file sizes before and after. If the WebP output is larger than the JPEG source, the source was already well‑compressed — don't convert. Drop the quality to 75–80 and retest; if it's still larger, keep the original.
Quick reference table
- PNG — lossless, transparent, best for UI/logos/screenshots with text.
- WebP — 25–35% smaller than JPEG, supports alpha, safe on modern web.
- AVIF — ~50% smaller than JPEG, HDR‑ready, slower to encode, spottier tooling.
- JPEG — still the universal fallback for email, legacy apps, and print.
AVIF encoding is CPU‑intensive. For large batches, convert to WebP first — it's fast and captures roughly 80% of AVIF's byte savings. Reserve AVIF for hero images and landing‑page heroes where every KB counts.