Lossy vs lossless: what you actually lose when you convert a file

The one rule that explains everything

There is a single idea behind every lossy-vs-lossless question: does the new format keep all of the original data, or does it throw some away to save space?

Lossless means the conversion preserves the data exactly. The format may pack the bits more cleverly, so the file size can change, but if you decode it back you get the identical pixels or audio samples you started with. Lossless is reversible in the sense that no information was lost along the way.

Lossy means the format deliberately discards data your eyes or ears are less likely to notice, in exchange for a much smaller file. The result looks or sounds close to the original, but it is not the original. Decoding a lossy file gives you an approximation, and the discarded data is unrecoverable.

That distinction is a property of the target format, not of any particular converter. JPG is lossy whether you make it in a browser, in a phone camera, or in professional software. The only thing a converter controls is whether it adds extra, unnecessary re-compression on top, and a privacy-first browser converter like hushvert does not: client-side pairs are encoded once, in your browser, with no hidden server round-trip.

Which common image formats are lossless vs lossy

Lossless image formats keep every pixel exactly:

- PNG: lossless, and the only mainstream web format that also stores transparency (an alpha channel). Great for screenshots, logos, diagrams, and anything with sharp edges or text. - TIFF: lossless, common in photography, scanning, and print workflows. - BMP: lossless and uncompressed, so files are large; mostly a legacy/Windows format.

Lossy image formats discard detail to shrink the file:

- JPG (JPEG): lossy, designed for photographs. Excellent for photos, poor for sharp text and flat color, and it has no transparency. - HEIC: the lossy format iPhones shoot in. Smaller than JPG at similar quality, but lossy. - WebP and AVIF at lossy settings: modern formats that beat JPG on size at a given quality. Note that WebP and AVIF can also run in a lossless mode; at their usual lossy settings they discard data like JPG does.

SVG is a special case: it is not pixels at all but vector instructions, so it scales to any size without quality loss. Converting a photo to SVG does not make it lossless; it just wraps or traces a raster image.

Which common audio formats are lossless vs lossy

Lossless audio formats keep every sample of the original recording:

- WAV: lossless and uncompressed, so files are large. The straightforward archival format. - FLAC: lossless and compressed. It is typically around half the size of the equivalent WAV while staying bit-for-bit identical when decoded. This is the format to use when you want lossless audio without WAV-sized files.

Lossy audio formats discard sound to shrink the file:

- MP3: the classic lossy format. Universally playable, small, and not lossless. - OGG (Vorbis), AAC, and M4A (which usually contains AAC): all lossy, all designed to sound good at small sizes.

A practical way to remember it: WAV and FLAC are the two you reach for when you cannot afford to lose anything; MP3, OGG, AAC, and M4A are the ones you reach for when small and convenient matters more than perfect.

Lossless to lossless: nothing is lost

When both the source and the target format are lossless, the conversion preserves the data exactly. Nothing is approximated.

- WAV to FLAC keeps every audio sample. You usually end up with a much smaller file, and if you ever convert that FLAC back to WAV you get an identical waveform. FLAC is just a better-packed container for the same sound. - PNG to TIFF, or PNG to BMP, keeps every pixel. The file size changes because the formats compress differently, but the image is identical.

On hushvert, these lossless-to-lossless conversions run entirely in your browser (audio and images are client-side pairs), the file bytes never leave your device, and there is no hidden extra server re-compression layered on. What you put in is exactly what comes out, just in a different wrapper.

Converting TO a lossy format: this is where you lose data

The moment your target format is lossy, the converter has to re-encode the file and throw data away. This is true even if your source was a pristine lossless original.

- PNG to JPG re-encodes the image as JPEG, which discards detail, and JPG has no transparency, so any transparent areas are flattened, usually onto a white or black background. You lose quality and the alpha channel. - WAV or FLAC to MP3 (or to OGG, AAC, or M4A) re-encodes the audio and permanently removes sound the encoder judges less audible. The result is smaller and convenient, but it is no longer lossless. - Any audio to MP3 re-encodes. There is no such thing as a lossless MP3.

This is not a flaw in a specific tool. It is what the format is. A higher quality setting (a higher JPG quality, a higher MP3 bitrate) loses less, and at high settings the difference can be hard to perceive, but it is still lossy. If you need the exact original data, you have to keep, or convert to, a lossless format.

Is FLAC to MP3 lossless? And does PNG to JPG lose quality?

These are the two most-asked versions of the same question, so to be direct:

FLAC to MP3 is not lossless. FLAC is a lossless format, but MP3 is lossy, so the conversion re-encodes the audio and discards sound permanently. The MP3 will sound close at a reasonable bitrate, and it will be far smaller and play anywhere, but it is a lossy copy. If you want a smaller lossless file instead, FLAC already is one. If you specifically need a lossless WAV, FLAC to WAV preserves the audio exactly because both are lossless.

PNG to JPG does lose quality, and it loses transparency. PNG is lossless; JPG is lossy and has no alpha channel. Converting re-encodes the image (discarding fine detail, often visible as halos around sharp text or edges) and flattens any transparent regions onto a solid background. For photos the quality loss is usually acceptable and the file gets much smaller. For screenshots, logos, line art, or anything with transparency, keep it as PNG, or use a lossless target.

Generational loss: why you should not re-encode lossy files over and over

Each time you save a lossy file as a new lossy file, the encoder throws away data again, on top of the data the previous round already removed. This compounding degradation is called generational loss.

If you take a JPG, edit it, re-save as JPG, send it, someone re-saves it as JPG again, and so on, the quality drops with every generation: blocky artifacts spread, colors smear, sharp edges blur. The same happens with audio: an MP3 re-encoded as a lower-bitrate MP3 a few times audibly degrades. Crucially, converting a lossy file to a lossless format does not undo the damage; PNG-from-a-JPG just stores the already-degraded image perfectly. The data was lost at the first lossy save.

How to avoid it:

- Keep a lossless master (PNG/TIFF for images, WAV/FLAC for audio) and export lossy copies from it as needed, rather than re-editing the lossy copies. - Do all your edits before the single lossy export, not after. - Convert lossy to lossless only when a tool requires a specific format, not as a way to recover quality, because it cannot.

Pick this when: practical guidance

Images:

- Photographs you want small and shareable: JPG, or WebP/AVIF for smaller files at similar quality. All lossy. - Screenshots, logos, diagrams, line art, or anything with text or sharp edges: PNG. Lossless, and it keeps transparency. - Anything that needs transparency: PNG, WebP, or AVIF, never JPG. - An editing or archival master you will export from repeatedly: PNG or TIFF.

Audio:

- Music or recordings for everyday listening on phones and players: MP3 (universal) or AAC/M4A and OGG (efficient). All lossy. - Archiving, mastering, or anything you may re-edit: WAV (uncompressed) or FLAC (lossless and roughly half the size of WAV). - You have WAV and want a smaller lossless file: convert to FLAC. Nothing is lost. - You have FLAC and need it to play everywhere: convert to MP3, accepting that it becomes lossy.

The short version: lossless when the data matters, lossy when size and convenience matter. On hushvert, all of the image and audio conversions above run client-side in your browser, free and unlimited, with the bytes never leaving your device, so the only thing that changes your file is the format you chose, not an upload pipeline you cannot see.

Conversions where lossy vs lossless matters

• PNG to WEBP
• JPG to PNG
• WAV to MP3
• HEIC to JPG
• MP4 to MP3

Keep reading

• Convert audio without uploading
• How hushvert keeps your files private
• What is HEIC?
• See the no-upload proof

Common questions

What is lossless conversion?

A lossless conversion changes a file's format while preserving every bit of the original data. The encoded bytes may be arranged differently and the file size may change, but decoding the result gives back the identical pixels or audio samples you started with. WAV to FLAC and PNG to TIFF are lossless: nothing is approximated or discarded.

What does lossy mean?

Lossy means the format deliberately discards some data to make the file smaller, keeping the parts your eyes or ears are least likely to miss. The result looks or sounds close to the original but is an approximation, and the discarded data cannot be recovered. JPG, HEIC, MP3, OGG, AAC, and lossy WebP/AVIF are lossy formats.

Does converting PNG to JPG lose quality?

Yes. PNG is lossless and JPG is lossy, so the conversion re-encodes the image and permanently discards detail, often visible as halos around sharp text or edges. JPG also has no transparency, so any transparent areas are flattened onto a solid background. For photos the trade is usually fine and the file shrinks a lot; for screenshots, logos, or anything with transparency, keep PNG.

Is converting FLAC to MP3 lossless?

No. FLAC is lossless but MP3 is lossy, so the conversion re-encodes the audio and removes sound permanently. The MP3 sounds close at a reasonable bitrate and plays everywhere, but it is a lossy copy. If you want lossless, FLAC already is one; FLAC to WAV stays lossless because both formats are.

Which image formats are lossless?

PNG, TIFF, and BMP are lossless: they keep every pixel exactly. PNG is the common web choice and is the only mainstream web format that also stores transparency. WebP and AVIF have a lossless mode too, but at their usual lossy settings they discard data like JPG.

Which image formats are lossy?

JPG (JPEG), HEIC, and WebP/AVIF at their usual lossy settings are lossy: they discard detail to shrink the file. JPG is built for photographs and has no transparency. HEIC is the smaller, lossy format iPhones shoot in.

Which audio formats are lossless?

WAV and FLAC are lossless. WAV is uncompressed, so files are large. FLAC is compressed but still bit-for-bit identical when decoded, typically around half the size of the equivalent WAV, which makes it the practical choice for lossless audio without WAV-sized files.

Which audio formats are lossy?

MP3, OGG (Vorbis), AAC, and M4A (which usually holds AAC) are lossy. They discard sound to stay small and convenient. They are excellent for everyday listening and universal playback but are not suitable as an archival master.

Does converting WAV to FLAC lose any quality?

No. Both WAV and FLAC are lossless, so the conversion keeps every audio sample exactly. You generally get a much smaller file, and converting that FLAC back to WAV reproduces an identical waveform. FLAC is just a better-packed container for the same sound.

Can I recover quality by converting a lossy file back to a lossless format?

No. Converting a JPG to PNG, or an MP3 to WAV, stores the already-degraded file perfectly but does not bring back the data the lossy format discarded. That data was lost at the first lossy save. A lossless copy of a lossy file is still missing whatever the lossy step removed.

What is generational loss?

Generational loss is the compounding quality drop that happens when you repeatedly save a lossy file as a new lossy file. Each re-encode discards more data on top of the last, so JPGs re-saved as JPGs (or MP3s re-encoded as MP3s) visibly or audibly degrade over time. Keep a lossless master and export lossy copies from it to avoid this.

How do I avoid generational loss?

Keep a lossless master (PNG or TIFF for images, WAV or FLAC for audio), do all your edits before a single lossy export, and avoid re-editing the lossy copies. Convert lossy to lossless only when a tool requires a specific format, not as an attempt to recover quality, because it cannot recover it.

Is a higher quality setting still lossy?

Yes. A higher JPG quality or a higher MP3 bitrate discards less data, and at high settings the loss can be hard to perceive, but the format is still lossy by definition. Only a lossless format guarantees the exact original data.

Is converting between two lossy formats lossless?

No. Converting one lossy file to another lossy format (for example MP3 to AAC, or JPG to WebP at lossy settings) re-encodes the file and discards data again, which adds a generation of loss on top of whatever the first lossy step already removed. It is best avoided when quality matters.

Why does JPG remove transparency?

The JPG format simply has no alpha channel; it cannot store transparency. When you convert a PNG with transparent areas to JPG, those areas are flattened onto a solid background color, usually white or black. If you need transparency, use PNG, WebP, or AVIF instead.

Is HEIC lossless?

No. HEIC is a lossy format. It stores photos at smaller sizes than JPG for similar visual quality, which is why iPhones use it, but it discards data like other lossy formats. Converting HEIC to JPG is a lossy-to-lossy step; converting it to PNG stores the decoded image losslessly but does not add back detail HEIC never kept.

What is the most efficient lossless format for photos and audio?

For images, PNG and TIFF are lossless; PNG is usually the more practical web choice and TIFF is common in print and scanning workflows. For audio, FLAC is the efficient lossless choice because it compresses to roughly half the size of WAV while staying bit-for-bit identical.

Is SVG a lossless image format?

SVG is a vector format, not a pixel format, so it scales to any size without quality loss. But converting a photo to SVG does not make a photo lossless; it just wraps or traces a raster image. SVG is for logos, icons, and illustrations made of shapes, not photographs.

Does hushvert add extra compression when it converts my file?

No. For its client-side image and audio pairs, hushvert encodes your file once in your browser using the format you chose, with no hidden extra server re-compression. Lossless-to-lossless pairs (like WAV to FLAC or PNG to TIFF) preserve the data exactly, and the file bytes never leave your device.

Are hushvert's lossless conversions free?

Yes. All of hushvert's client-side image and audio conversions, including lossless-to-lossless ones like WAV to FLAC, are free and unlimited with no account, because they run entirely in your browser. The paid lane is only for a few conversions a browser cannot do, such as office documents to PDF and large video.

Does the converter I use change whether a format is lossy?

No. Lossy or lossless is a property of the target format, not the converter. JPG is lossy and FLAC is lossless no matter what tool makes them. The only thing a converter controls is whether it adds extra unnecessary re-compression on top, which hushvert does not do on its client-side pairs.