How I Built 100+ Client-Side E-Commerce & Dev Utilities With Zero Server Storage

Muhammad Junaid — Sat, 14 Nov 2026 03:04:28 +0000

Most online calculators and PDF/image utilities upload your sensitive data—unit costs, ad spend, or private documents—to a backend server and clutter the screen with intrusive ads.

I built SwiftKitHub (swiftkithub.com) to solve this: a fast, 100% client-side utility workbench running entirely inside browser memory using React, TypeScript, and WebAssembly.

Architecture Highlights

0 KB Cloud Payload: All calculations, PDF merging, and image conversions run locally in the browser with zero server storage or tracking.
Deterministic 2026 Math: Verified against 400+ automated unit tests so sellers and media buyers get exact cent-accurate numbers.
Static Pre-Rendering: Built with Vite and statically pre-rendered across 136 routes for sub-second First Contentful Paint.

Flagship Tools You Can Try Free (No Signup)

E-Commerce & Marketplace Fees:
- Etsy Fee Calculator 2026 — Models transaction fees, listing fees, regulatory operating fees, and net margin.
- TikTok Shop US Fee Calculator — Calculates 6.0% referral tiers and affiliate commissions.
- Product Margin Calculator — Real landed COGS vs. gross/net margin breakdown.
Ad Spend & ROAS:
- Break-Even ROAS Calculator — Finds your exact survival ROAS floor and max CPA before spending on ads.
Media & Developer Utilities:
- 4:3 to 16:9 Aspect Ratio Converter — Instant pixel resolution scaling for video and screens.
- CSS Gradient Generator — Live linear and radial CSS code builder.

I'd love feedback from fellow builders on the UI, speed, and any edge-case calculators you'd find useful!

DEV Community: Muhammad Junaid

How I Built 100+ Client-Side E-Commerce & Dev Utilities With Zero Server Storage

Architecture Highlights

Flagship Tools You Can Try Free (No Signup)