DEV Community: Muhammad Zeeshan

Sample files — test files for bugs, not file sizes

Muhammad Zeeshan — Tue, 18 Aug 2026 13:49:46 +0000

A while back I was working on a video player inside an app. Basic stuff. Pick a file, play it. It worked on every file I threw at it, so I shipped it.

Few days later I received a bug report with screen recording. Black screen, audio playing fine, no video. The file was an MP4. My test file was also an MP4. Same extension, same container, completely different result.

The difference was the codec inside. His file was HEVC. Mine was H.264. I never tested that because I never had a file to test it with.

So I went looking for one.

What I found instead

If you search for sample video download, you land on sites like file-examples.com or filesamples.com. They are useful, and I have used them multiple times. But all the available variants are just size or resolution based:

MP4 / SD / 1.26 MB
MP4 / HD / 36.48 MB
MP4 / 4K / 66.41 MB

It answers two question:

how big is the file?
how crisp is it?

Its perfectly fine if you are testing an upload limit or how it looks in a high resolution device. It does not help at all when your player shows a black screen, because all provided files are of the same codec, the same frame rate, the same color tags. Downloading a bigger version of a file that already works tells you nothing new.

I wanted the opposite. I did not care about size or resolution. I cared about what was inside.

So I built Sample Files

Sample Files is a small tool on my site that gives you ready made test files, grouped by the situation and use cases you are testing instead of by how many kilobytes they are.

Sample file is not a file generator. You do not fill a form and press "Generate". Every file is already made, already checked, and sitting there waiting for you to download it. Open the format you need, read the short label on each file, grab the one that matches your case. Few variants have an info icon that shows any additional information about the use case.

Back to the video player. Under videos you get things like:

H.264 in MP4, the safe one that plays everywhere
HEVC, with and without the hvc1 tag, which is the exact reason some files play on iOS and Mac and some do not
AV1 and VP9, which QuickTime will politely refuse to open
Variable frame rate files, which quietly break seeking and duration maths
Different color space tags, so you can see if your player washes out the picture
Files with chapter markers
Files with two or three audio tracks, so you can build and test a track switcher
Files with metadata embedded, and files with none at all

Every one of those is a real bug I have either hit myself or watched someone else hit. That black screen I shipped? There is a file for it now.

55+ formats, not just video

MP4 is just where I started. The tool now covers 55+ formats, and a good number of them go far past the usual "here's a small one and a big one" treatment.

MOV has the same codec, frame rate and tagging depth as MP4.
RTF has files written by five different editors, plus spec version and encoding variants.
ZIP splits across compression methods, encryption types, Zip64, non-Latin filenames and a few deliberately broken archives.
TAR.GZ covers the old tar flavors, sparse files and path traversal cases.
PNG with its filter methods.
TIFF with its compression and layout variants
FLAC and Opus for audio, and CSV with the delimiter, encoding and quoting messes that wreck importers.

If you work with any of those, there is more waiting for you than a size list.

Go break something

It is free, there is no signup, and you download only the file you need instead of a giant bundle.

👉 mzeeshan.me/tools/sample-files

I am still adding formats and variants, so if you have hit a file that broke your app in a strange way, fill out the form on the page. If its a case that is beneficial for other users in general its exactly the kind of case I want to add next. Odds are good someone else has the same black screen sitting in their bug tracker right now.

Stop Using a Plain Image Resizer for Your App Icons — Here's What to Do Instead

Muhammad Zeeshan — Thu, 23 Apr 2026 10:27:50 +0000

Most "app icon generators" online are just glorified image resizers. You drop in a 1024×1024 PNG, they spit out smaller versions of the same file. That's it.

That works fine if your icon is already fully designed. But what if you're in the middle of building an MVP and just need something that looks like a real app?

The problem with placeholder icons

When you create a new iOS or Android project, the default placeholder is a gray grid. It's immediately recognizable as "this app is not finished." If you're demoing to a client, a stakeholder, or running a TestFlight build — that gray grid signals unpolished before anyone taps a single screen.

A real icon takes 5 minutes to set up. There's no reason to ship without one.

What your icon actually needs to output

iOS and Android have strict requirements, and they differ from each other.

iOS expects an AppIcon.appiconset folder with a Contents.json manifest so Xcode knows which file maps to which context. Sizes range from 20pt all the way to 1024pt, at @1x, @2x, and @3x scale.

Android uses adaptive icons — a foreground layer and a background layer rendered separately, so the system can apply its own mask (circle, squircle, rounded square, etc.) depending on the device manufacturer. You also need:

Legacy icons for API ≤ 25
Round icons for API 25
A 512×512 Play Store asset
Monochrome variant for Android 13+ themed icons

A plain image resizer gives you none of this structure. You'd still need to manually rename files, arrange folders, and write the Contents.json.

What actually helps

If you're inside the IDE

Android Studio Panda 3 have built-in adaptive icon builder.

Android Studio's Image Asset Studio covers the basics — foreground, background, monochrome, legacy, and round variants from a single dialog. Access it via right-click on res/ → New → Image Asset.

But it has few limitations:

The built-in clip art library is limited
There's no text styling (bold, italic, regular)
The UI can feel clunky for anyone who just wants a quick, clean result.

My tool addresses all of this — you get access to the full React Icons library (thousands of icons across Font Awesome, Material Design, Remix, and more), proper text styling options, a simpler interface, and a live device preview that shows your icon across all Android shape variants before you download anything.

Its a free browser-based tool that goes further than just resizing.

You can:

Layer assets — choose a foreground (image, clip art from thousands of React Icons, or styled text) over a custom background color or image
Preview in context — see your icon live in real iPhone and Android device frames across 8 real-world contexts: home screen, spotlight, settings, App Store, notifications, and more
Download a ready-to-use ZIP — with the correct Xcode AppIcon.appiconset folder structure and Android mipmap folders, ready to drop straight into your project

It's especially useful during active development because the assets are replaceable — swap out the foreground or background anytime as your branding evolves, without starting from scratch.

👉 mzeeshan.me/tools/app-icon-generator

The 2-minute MVP icon workflow

Pick any icon from the built-in React Icons library — or upload your own image or logo
Set a background color that matches your app's brand
Preview it on a home screen and adjust until it reads clearly at small sizes
Download the ZIP and drop the folders directly into Xcode or Android Studio

Your app won't look finished. But it'll look intentional — which is all you need for early builds, client demos, and internal testing.

Quick reference: what each platform needs

Asset	iOS	Android
Source size	1024×1024 PNG	512×512 PNG (Play Store)
Output format	AppIcon.appiconset + Contents.json	mipmap-mdpi through mipmap-xxxhdpi
Adaptive layers	✗	✓ Foreground + Background
Monochrome	✗	✓ Android 13+
Legacy fallback	✗	✓ API ≤ 25
Round icon	✗	✓ API 25

The gray grid is a 5-minute problem. No reason to leave it there.

Works for native iOS, Android, React Native, and Flutter projects.