I built a local-first image checker for marketplace sellers

#ecommerce #webdev #tools #indiehackers

Marketplace sellers often discover image problems too late.

A product photo may look fine in an editor, but after uploading it to a marketplace it can become:

cropped in search thumbnails
too small for zoom previews
the wrong aspect ratio for a sales channel
risky for Amazon-style main image requirements
awkward when reused across Etsy, Amazon, TikTok Shop, Shopify, eBay, or Walmart

I wanted a simple preflight step before publishing product images, so I built ListingPic:

👉 https://listingpic.com/

What it does

ListingPic is a browser-based marketplace image checker and resizer.

You upload a product photo, choose the marketplaces you care about, and get a readiness report covering things like:

image dimensions
aspect ratio
file type
file size
thumbnail crop risk
safe-area positioning
marketplace-specific warnings

The goal is not to replace manual review. It is to catch obvious image risks before sellers waste time uploading, previewing, deleting, resizing, and re-uploading.

Why local-first?

A lot of product photos are sensitive:

unreleased SKUs
private product photography
branded assets
client images
images sellers do not want copied or stored elsewhere

So ListingPic processes images locally in the browser.

Your images are not uploaded to our server for analysis.

That also makes the tool fast for quick checks: drop in an image, review the warnings, adjust before publishing.

Current checkers

The MVP includes marketplace-focused checks for:

general marketplace readiness
Etsy image checks
Amazon product image checks
TikTok Shop image checks

There are also entry points for Shopify, eBay, and Walmart workflows.

Example use case

Imagine you have one product photo and want to reuse it across multiple channels.

ListingPic can help answer:

Is the image large enough?
Will the product be cut off in thumbnails?
Is the image close enough to square for a channel that prefers square previews?
Is the product too close to the edge?
Do I need a separate crop for Etsy or TikTok Shop?
Do I need to manually review Amazon main image requirements?

What I learned while building it

A few product lessons stood out:

Sellers do not think in pixels first.

They think in terms like “will this upload?”, “will the product be cut?”, and “will this hurt my listing?”
Different marketplaces create hidden image work.

A single photo may need different crops or checks depending on where it is published.
Privacy matters even for small tools.

Local browser processing is a strong default for tools that touch product photos.
The hardest part is not just resizing.

It is explaining image risks in a way that non-technical sellers can act on quickly.