How to Convert BMP to AVIF: 5 Free Methods in 2026

Why Convert BMP to AVIF?

BMP (Bitmap Image File) is the oldest widely used image format still in active circulation. Developed by Microsoft in the late 1980s, BMP stores completely raw, uncompressed pixel data. No compression algorithm, no optimization — just pixels. A standard 1920×1080 screenshot in BMP format weighs approximately 6 MB. A larger diagram or legacy software export can run much higher.

AVIF (AV1 Image File Format) is the most advanced widely-supported image format available in 2026. Built on AV1 video codec technology, AVIF delivers compression that surpasses JPEG, PNG, and WebP simultaneously, while adding features like 10-bit color depth, HDR support, and film-grain synthesis. Converting BMP to AVIF is the single largest file size improvement you can make for any BMP image.

How much smaller? A typical 6 MB BMP screenshot becomes 150–500 KB as AVIF — a 90–97% reduction. AVIF lossy compression consistently outperforms WebP by 20–35% at equivalent visual quality. Even AVIF lossless produces files 80–85% smaller than BMP. No widely-supported format offers better compression from BMP.

Converting BMP to AVIF makes sense when you need:

If your BMP files will be edited further or used in design software, BMP to PNG is the better choice — PNG has universal software support and is lossless. For the smallest possible files headed to a website or app, AVIF wins decisively.

For the broader question of which format is best for the web, see our AVIF vs WebP vs JPEG comparison.

AVIF Quality Settings: CRF Explained

Unlike WebP (which uses a 0–100 quality scale), AVIF tools typically use a CRF (Constant Rate Factor) scale where lower numbers mean higher quality. Understanding this prevents common mistakes:

Practical recommendation: CRF 24–28 is the sweet spot for most BMP-to-AVIF conversions. It delivers visually indistinguishable quality from the original BMP while achieving 92–97% file size reduction. For screenshots and graphics with sharp edges and flat colors, use CRF 20–24 or lossless mode.

For FFmpeg specifically, the encoder speed is controlled with -cpu-used (0=slowest/best, 8=fastest/roughest). For web delivery, -cpu-used 4 balances quality and build time well.

Method 1: Convert BMP to AVIF in Your Browser (No Upload Required)

The fastest and most private method is a browser-based converter that processes your files entirely on your device. PhotoFormatLab's BMP to AVIF converter uses WebAssembly to convert BMP files locally — your images never leave your computer.

Step-by-step:

Why browser-based conversion matters for BMP files:

BMP files commonly originate from internal business software, legacy Windows applications, medical imaging systems, and screenshot tools. Uploading these files to server-based converters like Convertio, CloudConvert, or FreeConvert means your files transit to third-party servers — outside your control and potentially subject to retention policies.

For a full explanation of why browser-based conversion is safer than uploading, see our guide on converting images without uploading to a server.

Method 2: FFmpeg — Best Compression Control

FFmpeg is the most versatile media processing tool available across all platforms. It uses the libaom encoder for AVIF, which produces the best compression of any open-source AVIF encoder.

Install FFmpeg:

Convert a single BMP to AVIF (recommended quality):

```bash

ffmpeg -i input.bmp -c:v libaom-av1 -crf 28 -cpu-used 4 output.avif

```

Lossless AVIF with FFmpeg:

```bash

ffmpeg -i input.bmp -c:v libaom-av1 -crf 0 -cpu-used 4 output.avif

```

Batch convert all BMP files in a directory:

```bash

mkdir -p avif-output

for f in *.bmp; do

ffmpeg -i "$f" -c:v libaom-av1 -crf 28 -cpu-used 4 avif-output/"${f%.bmp}.avif"

done

```

Batch with higher quality (CRF 20):

```bash

mkdir -p avif-output

for f in *.bmp; do

ffmpeg -i "$f" -c:v libaom-av1 -crf 20 -cpu-used 4 avif-output/"${f%.bmp}.avif"

done

```

Note: AVIF encoding with libaom is CPU-intensive compared to JPG or WebP. On modern hardware, expect 1–5 seconds per image at -cpu-used 4. Using -cpu-used 6 or -cpu-used 8 speeds this up significantly at a modest quality trade-off — fine for bulk thumbnail generation.

Method 3: ImageMagick (Windows, Mac, Linux)

ImageMagick converts BMP to AVIF with simpler syntax than FFmpeg. Install via the ImageMagick website or on macOS with brew install imagemagick.

Convert a single file (ImageMagick 7):

```bash

magick input.bmp -quality 60 output.avif

```

Note: ImageMagick's -quality scale for AVIF maps differently than WebP. Quality 60 corresponds roughly to CRF 28 (good web quality). Quality 80 = CRF 20 (high quality). Quality 100 = near-lossless.

Batch convert all BMP files:

```bash

mkdir -p avif-output

for file in *.bmp; do

magick "$file" -quality 60 avif-output/"${file%.bmp}.avif"

done

```

Fast batch using mogrify:

```bash

mkdir -p avif-output

magick mogrify -format avif -quality 60 -path avif-output *.bmp

```

ImageMagick is the most convenient option when you need to combine conversion with other transformations — resize the image, apply sharpening, or adjust color profiles — all in a single command.

Method 4: Python Pillow

Pillow supports AVIF encoding on all platforms and is ideal for automated conversion pipelines, CI/CD workflows, or any scenario where BMP-to-AVIF is part of a larger processing chain.

Install Pillow:

```bash

pip install Pillow

```

Note: AVIF support in Pillow requires libavif to be installed on the system. On macOS: brew install libavif. On Linux: sudo apt install libavif-dev.

Convert a single BMP to AVIF:

```python

from PIL import Image

with Image.open('input.bmp') as img:

img.save('output.avif', 'AVIF', quality=60)

```

Batch convert with CMYK guard:

```python

from PIL import Image

import os

def convert_bmp_to_avif(input_dir, output_dir, quality=60):

os.makedirs(output_dir, exist_ok=True)

for filename in os.listdir(input_dir):

if filename.lower().endswith('.bmp'):

input_path = os.path.join(input_dir, filename)

output_path = os.path.join(

output_dir,

os.path.splitext(filename)[0] + '.avif'

)

try:

with Image.open(input_path) as img:

if img.mode not in ('RGB', 'RGBA'):

img = img.convert('RGB')

img.save(output_path, 'AVIF', quality=quality)

print(f'Converted: {filename}')

except Exception as e:

print(f'Error converting {filename}: {e}')

convert_bmp_to_avif('./bmp_files', './avif_files', quality=60)

```

The color mode guard converts CMYK BMP files (common from professional print workflows) and unusual palette-mode BMPs to RGB before encoding. AVIF requires RGB or RGBA input.

Method 5: Squoosh (Browser — Single Files)

Squoosh is Google's browser-based image optimization tool. It processes files locally (no uploads) and gives manual control over AVIF quality with a live preview comparison.

Steps:

Squoosh is best for single-file conversions where you want to visually compare quality levels before committing. For batch conversions, use PhotoFormatLab (Method 1) or the command-line methods above.

BMP vs AVIF: Feature Comparison

Key takeaways:

BMP to AVIF vs BMP to WebP vs BMP to PNG

Choosing the right output format from BMP depends on your destination and use case:

Convert BMP to AVIF when:

Convert BMP to WebP when:

Convert BMP to PNG when:

For more detail on the BMP to WebP conversion path, see our BMP to WebP guide. For lossless archiving decisions, see BMP to PNG.

Transparency in BMP to AVIF Conversion

Standard 24-bit BMP files have no alpha channel. Converting one of these to AVIF produces a fully opaque image — the background color in the BMP is preserved exactly. Transparency is not added automatically.

If you need transparency in the output:

32-bit BMP files with alpha: Some Windows applications (notably legacy video and imaging tools) save 32-bit BMP with an embedded alpha channel. FFmpeg and ImageMagick both preserve this alpha channel when encoding to AVIF. PhotoFormatLab's browser-based converter also handles 32-bit BMPs with alpha correctly.

Frequently Asked Questions

Does converting BMP to AVIF lose quality?

It depends on whether you use lossless or lossy AVIF. Lossless AVIF preserves every pixel from the BMP source exactly — zero quality loss, just dramatically smaller files. Lossy AVIF (CRF 24–28 in FFmpeg, quality 55–65 in ImageMagick) is visually indistinguishable from the original for most image types, including photographs and screenshots. AVIF's perceptual compression is particularly strong: at the same visual quality as WebP, AVIF files are 20–35% smaller. Always keep the source BMP if you need to re-export at a different quality later.

How much smaller will my AVIF file be compared to BMP?

For typical BMP files:

A 6 MB BMP screenshot typically becomes 100–400 KB as AVIF. Complex photographs with many colors and fine details compress less than flat graphics or screenshots. For comparison, the same image as WebP at equivalent quality is typically 20–35% larger than the AVIF version.

Is it safe to convert BMP files to AVIF online?

With PhotoFormatLab, yes — completely safe. All conversion runs in your browser using WebAssembly; your BMP files never leave your device. Server-based converters like Convertio, CloudConvert, and FreeConvert upload your files to remote servers, which is a real privacy risk for BMP files that may contain internal screenshots, scanned business documents, proprietary graphics, or sensitive system exports. Read our guide on whether online image converters are safe for a full breakdown.

What browsers support AVIF in 2026?

AVIF has approximately 94% global browser support as of 2026. All modern versions of Chrome (85+), Firefox (93+), Safari (16+), and Edge (121+) support AVIF natively. Internet Explorer does not support AVIF, but it is no longer supported by Microsoft. For the small percentage of users on older browsers, you can serve a WebP or JPG fallback using the HTML element. See our AVIF format guide for the full browser compatibility table.

Can I batch convert BMP files to AVIF?

Yes. PhotoFormatLab's BMP to AVIF converter accepts multiple files simultaneously and provides a ZIP download for the results — all processed privately in your browser. The bash loop examples in Methods 2 and 3 convert entire directories of BMP files. Python Pillow (Method 4) is ideal for automated pipelines where BMP-to-AVIF conversion is part of a larger workflow, such as a CMS image processing script or a CI/CD image optimization step.

Why is AVIF encoding slow compared to JPG or WebP?

AVIF uses the AV1 video codec as its compression engine, which is computationally heavier than the algorithms used by JPEG or WebP. The libaom encoder in FFmpeg in particular is designed for maximum compression efficiency, not encoding speed. For bulk conversions, use -cpu-used 6 or -cpu-used 8 in FFmpeg to speed things up at a modest quality trade-off. Alternatively, the browser-based PhotoFormatLab converter uses an optimized WebAssembly build that balances quality and speed for typical BMP file sizes.