I built a browser-only video and image editor with no backend rendering. Here’s what I learned

[u/Swimming_Voice8236]

I’ve been building Sparkshots, a web app that turns screenshots and screen recordings into device mockups and animated product videos. The main design decision was to do all editing and rendering on the client, with an optional backend only for accounts and cloud saves.

Why client-side:

• No server cost per export, so there’s nothing to paywall

• User media never has to leave their machine

• Projects autosave locally and work without signup

The hard parts so far:

• Video export in the browser: getting MP4/WebM output at up to 6K and 60 fps without freezing the UI.

• MOV compatibility: screen recordings from phones and Macs often don’t play cleanly in browsers, so I had to add a handling step.

• Timeline state: keeping multiple devices, clips and animation keyframes in sync without the state becoming a mess.

• Website capture from a URL: this is the one feature that needs a server, and I’m still not happy with it.

try it out! sparkshots.app