Why I Wrote This (And Why You're Probably Here)


Somewhere around the tenth time a friend texted me "hey quick question, how do I turn this PNG into a JPG," I figured I should just write it all down. Not because it's hard it isn't but because whenever someone Googles it, they land on some site covered in pop-up ads that makes them upload their file to a server they know nothing about, then wait through a "processing" spinner that may or may not finish.

I've been there myself. I once uploaded a video I really shouldn't have to a random converter site at 1am because I needed it in a different format by morning. So this is the guide I wish existed back then covering images, audio, and video, with the actual differences that matter instead of just a list of file extensions.

Image Conversion: PNG to JPG, JPG to PNG, and the Rest
Images are the conversion people run into the most, usually because they downloaded a screenshot, a logo, or a photo in the "wrong" format for whatever they're doing next.

PNG to JPG Converter — When You Actually Need This


PNG files are lossless and support transparency, but that also makes them heavy. If you're uploading a photo somewhere with a strict size limit, or you simply don't need the transparent background anymore, a PNG to JPG converter usually cuts the file size down a lot with no visible difference in a normal photo. I do this constantly with screenshots before emailing them nobody needs a 4MB PNG of a spreadsheet sitting in their inbox.

JPG to PNG Converter — The Other Direction


Going from JPG to PNG is less about file size and more about what you need next. If you're about to edit the image, layer it over something else, or need a transparent background, PNG is what you want. Just know that a JPG to PNG converter doesn't magically add transparency back JPG never had it in the first place but you do get a lossless copy to work with going forward, which matters if you'll be saving it multiple times while editing.

What About WEBP, GIF, BMP, TIFF, AVIF, and ICO?


These come up less often, but each has its moment:

+ WEBP is what a lot of websites use now because it's smaller than JPG or PNG at similar quality — worth converting to JPG or PNG if an app doesn't support it yet.
+ GIF usually needs to become a PNG or JPG when you just want one frame as a still image.
+ BMP and TIFF show up from scanners, old software, or design tools — converting to JPG makes them actually shareable.
+ AVIF is the newest and smallest format, but not every app opens it yet, so converting to JPG or PNG is the safe move.
+ ICO files are basically app icons and favicons in disguise — convert to PNG if you want to actually edit one.
+ And yes, JPG and JPEG are the exact same format with two different file extensions, so converting between them is really just a rename with extra steps — though it's a surprisingly common search.
+ Audio Conversion: MP3 to WAV, MP3 to AAC, and Everything In Between
 
Audio conversion questions usually come from one of two places: someone's editing something and needs an uncompressed file, or someone has a file their phone, car, or old speaker system just won't play.

MP3 to WAV Converter (and Back Again)

 
WAV is uncompressed audio, so it's the format editors and audio software prefer no compression artifacts to fight with. I convert MP3 to WAV whenever I'm about to do anything serious in an audio editor, then convert back with a WAV to MP3 converter once I'm just sending the finished file to someone. A full WAV file for a three-minute clip can be ten times the size of the MP3 version, for no audible difference in everyday listening.

MP3 to AAC Converter — The One Apple Users Ask About

AAC tends to sound slightly better than MP3 at the same file size, and it's the default format for a lot of Apple devices and services. If something sounds "off" after moving a file onto an iPhone or into GarageBand, converting MP3 to AAC or the reverse, AAC to MP3, if you're heading the other way usually clears it up.

FLAC, OGG, M4A, WMA, OPUS, and AIFF — The Supporting Cast


+ FLAC to MP3 — for when you have a lossless archive copy but need something smaller to actually put on your phone.
+ M4A to MP3 — extremely common for voice memos recorded on an iPhone that need to go anywhere else.
+ OGG to MP3 and WMA to MP3 — usually old files (OGG from games, WMA from ancient Windows Media Player rips) that just need modernizing.
+ MP3 to OPUS — if you want the smallest possible file size at a quality that still sounds genuinely good, OPUS is worth the switch.
+ AIFF shows up mostly in professional audio work — converting MP3 to AIFF (or back to MP3) covers the handful of times you actually need it.
+ Video Conversion: MP4 to AVI, MOV to MP4, and the Codec Headache
+ Video is where people get the most frustrated, mostly because "it won't play" can mean five completely different things.

MP4 to AVI Converter

AVI is an older container format that some editing software and older TVs still expect. Converting MP4 to AVI, or going the other way with an AVI to MP4 converter, is usually about compatibility with something older rather than quality MP4 is generally the better everyday format if you have the choice.

MOV to MP4 Converter — The iPhone Problem

This is probably the single most common video conversion request that exists. iPhones and Macs record and export in MOV by default, and it plays perfectly everywhere in the Apple ecosystem and almost nowhere else. Running it through a MOV to MP4 converter before uploading somewhere or sending it to a non-Apple device will save you the confused "it says the file isn't supported" text from a friend.

MKV, WEBM, FLV, WMV, 3GP, MPEG, and M4V — Quick Notes

 
+ MKV to MP4 — MKV can hold multiple audio tracks and subtitles, which is great until an app or TV just refuses to open it. MP4 is the safer bet for playback.
+ MP4 to WEBM — mostly a web-developer thing; WEBM is lighter for websites but not something you'd want sitting on a random device.
+ FLV to MP4 — a relic of the old Flash-video era that still shows up in old downloads.
+ WMV to MP4 — classic Windows Movie Maker exports, converting makes them playable on literally anything.
+ 3GP, MPEG, and M4V — mostly older phone recordings or specific device exports; MP4 is almost always the better destination format.
 

Why I Stopped Using Random "Free Converter" Websites

 
Here's the part that isn't really about formats. A few years back I needed to convert a video quickly, searched for an "mp4 to avi converter," clicked the first result, and uploaded a video I really shouldn't have handed over to a server I knew nothing about. It converted fine. It also sat on their server for who-knows-how-long afterward, and I had no real way to know what happened to it next.

That's the whole reason this site works the way it does. Every conversion image, audio, or video happens directly in your browser, using your own device's processing power. Nothing gets uploaded anywhere. If your internet drops halfway through a conversion (after the page itself has loaded), the conversion still finishes, because there's no server doing the work in the first place. It's a bit slower for genuinely huge files than a beefy server farm would be, sure, but I'll take "a little slower" over "my files went somewhere I can't see" every single time.

My Quick Cheat Sheet

If you just want the short version, here's what I tell people:

1. Sending a photo and size matters: use a PNG to JPG converter.
2. About to edit an image: use a JPG to PNG converter.
3. Editing audio seriously: convert MP3 to WAV.
4. Sending a finished audio file: WAV to MP3, or MP3 to AAC for Apple devices.
5. Video won't play on someone else's device: convert it to MP4, no matter what it started as MOV to MP4, MKV to MP4, and AVI to MP4 are the three you'll need most.
6. Old file from a dead app or device: convert it to whatever's most common now (JPG, MP3, or MP4) and stop worrying about it.
 

Final Thoughts


None of this is complicated once you know the "why" behind each format it's just that nobody ever explains the why, they just say "click convert" and hope for the best. Hopefully next time someone texts you "how do I turn this into an MP4," you can send them this instead of quietly doing it for them. Or, more realistically, you'll still do it for them anyway but at least now you'll know exactly why.