AVIF to WebP Converter Online — Modern-to-Modern Format Bridge

Q: Will the WebP be smaller than the source AVIF?

No, typically the WebP will be larger. AVIF's AV1 codec (AOMedia Bitstream Spec v1.0.0, 25 June 2018) uses more sophisticated intra-prediction and entropy coding than WebP's VP8 (RFC 6386 Bankoski et al., November 2011), giving AVIF a ~20–40% size advantage at equivalent visual quality. Expect 1.5–2× size growth converting AVIF → WebP. The conversion is appropriate when broader browser compatibility outweighs the size cost — e.g., serving the same image to Safari 14–16.3 users who cannot decode AVIF.

Q: Does transparency survive AVIF → WebP conversion?

Yes, both formats support 8-bit alpha. AVIF carries alpha as an auxiliary image item per ISO/IEC 23008-12 HEIF; WebP supports alpha via the ALPH chunk per RFC 9649 §2.7.1.2. The Canvas 2D Context conversion preserves alpha bytes exactly: decode AVIF → ImageBitmap with alpha → drawImage → toBlob('image/webp', quality) retains every transparent pixel. Note: AVIF 10-bit alpha is downconverted to 8-bit since standard browser Canvas operates at 8-bit precision.

Q: Should I use lossy or lossless WebP for converting AVIF?

Depends on AVIF source. Lossy AVIF sources (typical web-served AVIF) should convert to lossy WebP at quality 80–85 — re-encoding AV1's already-quantised pixels into WebP lossless would 2–3× the file size with no fidelity gain. Lossless AVIF sources (rare — typically design-tool exports for archival) can convert to lossless WebP (quality=100, or quality=1.0 in Firefox 105+) — preserves every pixel exactly. The pragmatic default is lossy WebP at quality 85 since most AVIF in the wild is already lossy.

AVIF to WebP Converter — Bridging Two Modern Formats

AVIF (AV1 Image File Format, AOMedia v1.2.0; ISO/IEC 23000-22:2019 MIAF (first edition June 2019)) and WebP (RFC 9649 Zern, Massimino & Alakuijala, Google LLC, November 2024) are both modern image formats with excellent compression. AVIF typically compresses 20–40% smaller than WebP at equivalent visual quality (up to ~50% on some content) thanks to AV1's more sophisticated encoding (AOMedia Bitstream Spec v1.0.0, 25 June 2018), but WebP has broader browser support — Safari decoded WebP since version 14 (16 September 2020), added still AVIF in iOS 16.0 (September 2022), and full AVIF (animation/grid/sequences) in 16.4 (March 2023). Convert AVIF → WebP when you need wider browser compatibility (especially Safari 14.0–15.x users with no AVIF support) without falling back to JPEG, accepting some size growth as the cost of compatibility. Browser asymmetry: AVIF decoding requires Chrome 85+, Firefox 93+, or Safari 16.4+; WebP encoding via Canvas toBlob is native in Chrome 18+ / Edge 79+ / Firefox 96+ but Safari requires a libwebp WebAssembly polyfill — so Safari users hit the WebP encoding limitation even though they can decode AVIF.

How to convert AVIF to WebP

Drop an .avif file onto the tool or click to browse — single file or batch. Requires Chrome 85+, Firefox 93+, or Safari 16.4+ for AVIF decoding.
Pick a WebP quality level (1–100). 80–85 is the safe sweet spot for photos; lossless via quality=1.0 (Firefox 105+) or quality=100 elsewhere.
Watch the size comparison — typical WebP output is 1.5–2× larger than source AVIF for photos (the inverse of AVIF's compression advantage).
Download the WebP. Note: if you're on Safari, the conversion uses a libwebp WebAssembly polyfill since Safari doesn't support native WebP encoding.

Common use cases

Serving the same image to Safari 14.0–15.x users (who can read WebP but not AVIF) and AVIF-capable users (Safari 16.0+) via HTML <picture> source set.
Migrating an AVIF asset library to WebP-only when target audience includes meaningful pre-Safari-16.4 share.
Producing WebP fallbacks from AVIF for CMSes that haven't updated their image-handling pipelines to AVIF.
Preparing email attachments where WebP (broader desktop client support since 2020) works but AVIF (limited desktop email support) doesn't.

Frequently asked questions

What is AVIF and why convert to WebP?

AVIF (AOMedia v1.2.0; ISO/IEC 23000-22 MIAF) and WebP (RFC 9649 Nov 2024) are both modern formats. AVIF compresses ~50% better but has narrower browser support — Safari added still AVIF in iOS 16.0 (Sept 2022) and full AVIF in 16.4 (March 2023). WebP broader (Safari 14+ since 16 September 2020). Convert when wider compatibility outweighs size.

Will the WebP be smaller than the source AVIF?

No, typically larger. AVIF's AV1 codec (AOMedia v1.0.0, 25 June 2018) uses more sophisticated intra-prediction and entropy coding than WebP's VP8 (RFC 6386 Bankoski et al., Nov 2011), giving AVIF ~20–40% size advantage. Expect 1.5–2× growth converting AVIF → WebP.

Does transparency survive AVIF → WebP conversion?

Yes, both support 8-bit alpha. AVIF carries alpha as auxiliary image item per ISO/IEC 23008-12 HEIF; WebP supports alpha via ALPH chunk per RFC 9649 §2.7.1.2. Canvas conversion preserves alpha bytes exactly. AVIF 10-bit alpha downconverted to 8-bit since Canvas operates at 8-bit precision.

Does Safari work for this conversion?

Partially. Safari iOS 16.0+ (still AVIF, September 2022), Safari 16.4+ (full AVIF, March 2023) can decode AVIF — that part works. However, Safari does NOT support image/webp output via canvas.toBlob() — WebKit limitation. Safari users get AVIF read but need libwebp WebAssembly polyfill for WebP write. Chrome 85+ / Firefox 96+ / Edge 79+ handle both directions natively.

Should I use lossy or lossless WebP for converting AVIF?

Depends on AVIF source. Lossy AVIF (typical web-served) → lossy WebP at quality 80–85 — re-encoding AV1's quantised pixels into lossless WebP would 2–3× the file size with no fidelity gain. Lossless AVIF (rare) → lossless WebP (quality=100, or quality=1.0 in Firefox 105+). Pragmatic default: lossy quality 85.

Why bridge two modern formats — and the Safari limitation

AVIF and WebP serve overlapping but distinct compatibility profiles. AVIF's AV1 codec compresses ~50% better than WebP's VP8 (RFC 6386 Bankoski et al., November 2011) thanks to recursive partitioning, sophisticated intra-prediction, and arithmetic entropy coding versus VP8's earlier prediction modes. But AVIF support arrived later: Chrome 85 (Aug 2020), Firefox 93 (Oct 2021), Safari 16.4 (March 2023). WebP support is broader: Chrome 32+ (2014), Firefox 65+ (Jan 2019), Safari 14+ (16 September 2020). Safari users on 14.0–15.x (a meaningful audience segment in 2026) can read WebP but not AVIF; Safari 16.0–16.3 users can read still AVIF but not animated AVIFs — converting AVIF → WebP serves them without falling back to bulkier JPEG. Both formats support 8-bit alpha (AVIF auxiliary image item per ISO/IEC 23008-12 HEIF; WebP ALPH chunk per RFC 9649 §2.7.1.2), so transparency round-trips cleanly. The conversion runs locally via WHATWG Canvas 2D Context + HTMLCanvasElement.toBlob('image/webp', quality). Critical Safari note: while Safari 16.4+ can decode AVIF, Safari does NOT support image/webp output via canvas.toBlob — a long-standing WebKit limitation. Safari users converting AVIF → WebP need a JavaScript polyfill (typically libwebp compiled to WebAssembly) for the WebP encode step. Chrome 85+ / Firefox 96+ / Edge 79+ handle both directions natively. Expected size: WebP output 1.5–2× larger than source AVIF for photographs, the inverse of AVIF's compression advantage.

AVIF source decoded per AOMedia AV1 Image File Format spec v1.2.0
AV1 codec decoding per AOMedia Bitstream Spec v1.0.0 (25 June 2018)
Output WebP per RFC 9649 (Nov 2024 — VP8 lossy mode + lossless modes)
Adjustable WebP quality 1–100; lossless via quality=1.0 (Firefox 105+) or quality=100
Alpha channel preserved end-to-end (AVIF auxiliary image item → WebP ALPH chunk per RFC 9649 §2.7.1.2)
Browser-native encoding in Chrome 85+ / Firefox 96+ / Edge 79+; Safari requires libwebp polyfill for WebP output

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Sources (6)

Alliance for Open Media (AOMedia) — Storage and Transport Format WG (2024). AV1 Image File Format (AVIF). AOMedia specification v1.2.0 (aomediacodec.github.io/av1-avif/); also formalised in ISO/IEC 23000-22:2019 MIAF (first edition June 2019) — HEIF-derivative container with AV1 payload.
AOMedia Codec Working Group (2018). AV1 Bitstream & Decoding Process Specification. AOMedia v1.0.0 (25 June 2018; v1.0.0-errata1 8 January 2019) — open royalty-free video codec underlying AVIF stills.
ISO/IEC JTC 1/SC 29/WG 11 (MPEG) (2017). Information technology — High efficiency coding and media delivery in heterogeneous environments — Part 12: Image File Format (HEIF). ISO/IEC 23008-12:2017 (first edition) / 2022 (second edition) / 2025 (third edition) — base container that AVIF derives from; alpha channel carried as auxiliary image item.
Zern, J., Massimino, P., & Alakuijala, J. (Google LLC) (2024). WebP Image Format. RFC 9649, IETF (November 2024, Informational) — target WebP container with alpha-preserving lossy mode (VP8) or lossless mode (LZ77 + Huffman).
Bankoski, J., Koleszar, J., Quillio, L., Salonen, J., Wilkins, P., & Xu, Y. (Google Inc.) (2011). VP8 Data Format and Decoding Guide. RFC 6386, IETF (November 2011, Informational) — VP8 keyframe bitstream used by WebP lossy mode.
WHATWG (live). HTML Living Standard — Canvas 2D Context + HTMLCanvasElement.toBlob(). html.spec.whatwg.org/#2dcontext (browser AVIF decoding: Chrome 85+, Firefox 93+, Safari 16.4+; WebP encoding native in Chrome 18+ / Edge 79+ / Firefox 96+; Safari does NOT support image/webp output via toBlob — requires libwebp WebAssembly polyfill on Safari).

These are the W3C, ISO/IEC, ITU-T, and IETF specifications the tool implements or builds on. Locate them on w3.org, iso.org, itu.int, or datatracker.ietf.org.