Lossless vs. Lossy Compression: What You Should Know (2025 Guide)

Date published: October 22, 2025
Last update: September 13, 2025
Author: Marek Hovorka

Category: Image Formats Explained
Tags: Compression guide, File size optimization, FLAC vs MP3, Image compression, JPG vs PNG, Lossless compression, Lossy compression

What’s the difference between lossless and lossy compression? This guide explains how they work, with examples, advantages, and tips for choosing the right format.

Every image, video, or audio file you use has one thing in common: it takes up storage space. To make files smaller and easier to share, we use compression. But not all compression works the same way.

There are two main approaches:

• Lossless compression – keeps all the original data.
• Lossy compression – removes some data permanently to shrink the file size.

Understanding the difference is crucial if you want to choose the right format for your photos, designs, or web projects.

In this article, we’ll explain how each method works, their advantages and disadvantages, and which one you should pick depending on your needs.

What is Lossless Compression?

📖 Definition

Lossless compression is a method that reduces file size without removing any data. When you decompress the file, you get the exact original file back, bit for bit.

This makes lossless formats ideal for situations where accuracy and quality must be preserved.

⚙️ How it works

Lossless compression doesn’t throw away information — instead, it uses clever algorithms to store data more efficiently:

• Pattern recognition – repeating elements (like colors or text) are stored once and referenced multiple times.
• Dictionary methods – common sequences are replaced with shorter codes.
• Entropy coding – compresses frequent patterns more efficiently.

Example: Instead of saving “blue pixel” 100 times, the algorithm may save it once and simply record “repeat 100”.

📂 Examples of lossless formats

• Images: PNG, TIFF, BMP, GIF
• Audio: FLAC, ALAC (Apple Lossless)
• Video: Some professional editing codecs (e.g., Apple ProRes in lossless mode)
• Other files: ZIP, RAR, GZ archives

✅ When to use lossless

• Editing graphics, audio, or video (no data lost after multiple saves)
• Logos, icons, or text-based images (where sharpness matters)
• Archiving data where accuracy is critical

What is Lossy Compression?

📖 Definition

Lossy compression reduces file size by permanently removing some data that is considered less important.
When the file is decompressed, it does not fully match the original — instead, it’s a close approximation designed to look or sound the same to human senses.

⚙️ How it works

Lossy algorithms take advantage of the limitations of human perception:

• In images, we are more sensitive to brightness than to small color changes.
• In audio, we hear certain frequencies better than others.

The compression process:

1. Analyzes data (image/audio/video).
2. Removes details unlikely to be noticed.
3. Applies strong mathematical compression to shrink the file further.

Result: much smaller files, but with some loss of quality.

📂 Examples of lossy formats

• Images: JPG, WebP (in lossy mode), HEIC, AVIF
• Audio: MP3, AAC, OGG
• Video: MP4 (H.264), HEVC (H.265), AV1

❌ Downsides

• Quality can degrade noticeably at high compression levels.
• Repeated saving → cumulative damage (called generation loss).
• Not suitable for professional editing workflows.

✅ When to use lossy

• Everyday web images (fast loading, small size).
• Music streaming (MP3, AAC).
• Online video (YouTube, Netflix).
• Social media uploads.

Lossless vs. Lossy: Key Differences

🆚 Core Concept

• Lossless → no information is lost, original file can be perfectly restored.
• Lossy → some information is discarded forever, only an approximation of the original remains.

📊 Comparison Table

Feature	Lossless Compression	Lossy Compression
Quality	100% identical to original	Slight to significant loss
File Size	Larger	Much smaller
Use Case	Archiving, editing, logos, documents	Photos, music, video, web
Transparency Support (images)	Yes (PNG, TIFF)	No (JPG, most lossy formats)
Editing	Safe to re-edit multiple times	Degrades with each save
Examples	PNG, FLAC, ZIP	JPG, MP3, MP4

📌 When Lossless Wins

• Storing master copies of data.
• Professional editing (graphic design, audio engineering).
• Situations where accuracy is non-negotiable (medical scans, legal docs).

📌 When Lossy Wins

• Online streaming (YouTube, Spotify, Netflix).
• Web images where speed matters more than perfect fidelity.
• Sharing files quickly without worrying about storage limits.

👉 In short: lossless = precision, lossy = efficiency.

Practical Examples of Lossless vs. Lossy

🖼 Images

• Lossless (PNG, TIFF):
  • A logo with sharp edges and text will look crisp and clean.
  • Every pixel is preserved exactly.
• Lossy (JPG, WebP lossy):
  • A photo of a sunset may look the same to the eye, but fine textures (like clouds or gradients) are simplified.
  • At high compression, artifacts appear: blockiness, blur, or halos around edges.

🎵 Audio

• Lossless (FLAC, ALAC):
  • A song is preserved exactly as recorded in the studio.
  • Audio engineers use this for editing and mastering.
• Lossy (MP3, AAC):
  • Streaming services reduce file sizes by cutting frequencies most listeners won’t notice.
  • On cheap headphones, differences are small. On high-end speakers, you may hear distortion or missing detail.

🎞 Video

• Lossless (used in professional editing):
  • Every frame is intact, allowing color grading and effects with no loss.
  • File sizes are huge (minutes of footage = gigabytes).
• Lossy (MP4, HEVC, AV1):
  • Platforms like YouTube or Netflix rely on lossy codecs to stream HD/4K efficiently.
  • The result looks almost identical but uses 90% less storage.

⚡ Real-world analogy

• Lossless = photocopying a document perfectly.
• Lossy = summarizing the document to make it shorter → you keep the meaning, but some details are gone forever.

Advantages & Disadvantages of Lossless vs. Lossy

✅ Advantages of Lossless Compression

• Perfect quality (no data loss).
• Safe for multiple edits — no generation loss.
• Supports special features like transparency (PNG).
• Essential for archiving and professional workflows.

❌ Disadvantages of Lossless Compression

• Larger file sizes.
• Slower to transmit or upload.
• Not always necessary if perfect fidelity isn’t required.

✅ Advantages of Lossy Compression

• Much smaller file sizes.
• Faster uploads, downloads, and streaming.
• Good balance between quality and efficiency at medium settings.
• Universal support across web, social media, and mobile devices.

❌ Disadvantages of Lossy Compression

• Permanent quality loss (cannot recover discarded data).
• Multiple saves = cumulative damage.
• Artifacts can appear at higher compression levels.
• Not suitable for logos, text, or professional editing.

⚖️ Quick takeaway

• Lossless = precision, editing, archiving.
• Lossy = efficiency, sharing, web use.

How to Choose the Right Compression

Choosing between lossless and lossy isn’t just a technical question — it depends on what you’ll be using the file for.

📸 For Images

• Use lossless (PNG, TIFF): logos, icons, diagrams, text-based graphics, editing masters.
• Use lossy (JPG, WebP lossy, AVIF lossy): everyday photos, blog images, e-commerce product pictures, social media.

🎵 For Audio

• Use lossless (FLAC, ALAC): archiving music, professional editing, audiophile playback.
• Use lossy (MP3, AAC, OGG): streaming, portable players, casual listening.

🎞 For Video

• Use lossless (ProRes, FFV1): editing, film production, high-end archiving.
• Use lossy (MP4, HEVC, AV1): YouTube, Netflix, video calls, sharing online.

🌐 For the Web

• Lossy compression almost always wins: smaller sizes = faster websites, better SEO, and improved user experience.
• Progressive JPGs, WebP, and AVIF give the best balance between quality and performance.

⚡ Pro Tip (PixConverter)

If you’re unsure:

• Convert to lossless when you want to preserve details for editing.
• Convert to lossy when your priority is sharing, speed, or saving space.

PixConverter lets you switch easily between formats like JPG, PNG, WebP, and AVIF — so you can pick the right compression for the right job.

Frequently Asked Questions (FAQ)

❓ What is the difference between lossless and lossy compression?

• Lossless keeps all the original data, file can be perfectly restored.
• Lossy removes some data permanently to reduce file size.

❓ Which is better: lossless or lossy?

Neither is universally better — it depends on the use case.

• Lossless is better for editing, archiving, and precision.
• Lossy is better for sharing, streaming, and saving space.

❓ Do JPGs use lossy or lossless compression?

JPG uses lossy compression by default. However, some modern formats like WebP and AVIF support both modes.

❓ Can I convert a lossy file back to lossless?

No. Once data is lost in a lossy file, it cannot be restored. You can only convert to a lossless format to stop further quality loss.

❓ Is PNG lossless or lossy?

PNG is a lossless format, which is why it’s often used for graphics, logos, and images requiring transparency.

❓ Why does my image lose quality after multiple saves?

This happens with lossy formats like JPG, where each save introduces new compression artifacts. Use lossless for editing, and export to lossy only at the end.

❓ Which audio formats are lossless?

FLAC, ALAC, and WAV are examples of lossless audio. MP3 and AAC are lossy.