Shopify spy extensions compared: what each one can actually prove
Most Shopify research extensions answer the same three questions — what is this store selling, what is it charging, and what software is it running. They differ enormously in what they ask for in return, and in whether their headline numbers are measured or estimated.
The short answer
No browser extension can read a competitor's real sales, revenue, traffic or ad spend — none of that is present in a public storefront. Everything in this category is either reading what the page already served (apps, theme, prices, best-seller order, publish dates) or estimating from those signals on a server. Knowing which you are looking at is the whole decision.
How to check any of this yourself. Open an extension's
Chrome Web Store page and read the grey permission line under the install
button, or go to chrome://extensions → Details → Site access.
Every permission claim below is taken from the extension's own published
manifest and is visible to you in under a minute. We build one of these
tools, so verify rather than take our word for it.
What each tool asks to access
Permissions are the most useful comparison axis because they are public, unambiguous, and set by the developer. A tool that reads Shopify storefronts does not structurally need access to every site you visit.
| Extension | Runs on | Notable permissions | Package size |
|---|---|---|---|
| MurmSpy | Shopify + TikTok Shop only | storage, activeTab, scripting |
~0.24 MB |
| Koala Inspector | All sites | identity, identity.email, tabs, declarativeNetRequest, contextMenus |
~17.7 MB |
| PPSPY | All sites | storage |
~44.2 MB |
| Shoper Spy | Own domain | identity, identity.email |
~7.3 MB |
| UniSpy | All sites | identity, tabs |
~3.8 MB |
Read from each extension's published manifest, July 2026. "Runs on" is the content-script match pattern — what Chrome describes to you as "read and change your data on" those sites. Versions change; re-check before relying on it.
Measured versus estimated
The single biggest difference between these tools is what happens behind the headline number. Server-backed tools compute sales estimates you cannot inspect. Client-side tools can only report what the storefront served, which is less — but checkable.
| Capability | Client-side tools | Server-backed tools |
|---|---|---|
| Apps & theme installed | Yes — read from the page | Yes |
| Prices, discounts, catalog | Yes — public JSON | Yes |
| Best-seller order | Yes — the store's own sort | Yes |
| Launch cadence | Yes — publish dates | Yes |
| Sales / revenue estimates | No — not in public data | Estimated, method not visible |
| Traffic estimates | Only via a public API (e.g. Chrome UX Report) | Estimated or resold |
| Your browsing stays private | Yes — nothing leaves the device | Requests go to their server |
Which to choose
Choose a server-backed tool
If a sales or revenue estimate is the thing you actually want, and you accept that you cannot audit how it was produced. PPSPY and similar tools have far larger user bases and longer track records than we do. Treat their revenue figures as directional — independent comparisons of these estimates routinely disagree with each other.
Choose a client-side tool
If you want to see the store's actual stack, pricing structure and release rhythm without granting all-sites access or sending your browsing to anyone. You give up invented sales numbers. MurmSpy is the strict version of this: scoped permissions, no server, no affiliate links, every derived figure labelled with its method.
Head-to-head pages
- MurmSpy vs Koala Inspector — the app & theme detector comparison
- MurmSpy vs PPSPY — measured data vs sales estimates
MurmSpy
Shopify and TikTok Shop research with scoped permissions, no server, and honestly-labelled numbers. Free tier is permanent.