Grailed Plus

Period

2026

Contribution

Design and product development

Status

Published Chrome extension; Firefox build support

Pricing context and cross-market comparison inside the Grailed pages people already browse.

A listing rarely gives a buyer enough context to judge its price. Similar items appear on other marketplaces under different titles, and price history helps only when its limits are clear. I built Grailed Plus to bring marketplace comparison, local image matching, price history, currency conversion, and interface customization into the pages people already browse. The current application source is private; this article and the product demos provide a public explanation of the architecture and its tradeoffs.

Useful results before inference finishes

Comparison starts with listing metadata: title, product type, brand, and the available marketplace details. Results are partitioned by confidence. A photograph of the wrong product type should not outrank a credible match just because it looks similar.

A second pass uses MobileCLIP-S1 image embeddings to refine a bounded shortlist. ONNX Runtime runs in an extension worker, keeping inference off the page renderer. Preliminary results stay visible while scores arrive, and the ranking updates progressively. If inference fails or reaches its budget, the metadata results remain usable. Navigation invalidates work that belongs to an earlier listing.

For the implementation reviewed in October 2026, optional refinement has a 30-second maximum budget starting when preliminary results render. Visual similarity contributes up to 20 points, while confidence groups remain intact. These are source parameters, not measured latency or evidence of better relevance. They should be checked against a particular store release before treating that package as identical to the reviewed implementation.

Where the work runs

The browser extracts the active listing and displays comparison results. The worker computes embeddings locally. Depop retrieval still makes remote requests; eBay retrieval goes through a separate Node.js gateway that keeps API credentials out of the distributed extension. The gateway handles OAuth token reuse, category resolution, and text and image searches.

Category resolution and image search are optional improvements. Their failure falls back to text results. Local inference therefore describes one part of the system: eBay image search can send listing-image data through the gateway, and marketplace retrieval is not offline.

A regression worth protecting

A late score from a previous listing must not replace the current listing's results. The controller invalidates obsolete requests and applies refinements to the active request. Its regression suite also exercises streamed scores before final completion, exhaustion of the refinement budget, and preservation of confidence groups when visual scores change the order within a group.

The relevant private-source modules are marketCompareController.ts and imageSimilarity.ts; marketCompareController.test.js asserts that streamed scores affect the visible results before the refinement promise resolves. This explains the tested contract without advertising an inaccessible source link or presenting the client suite as validation of the separate gateway.

The gateway follow-up has its own offline tests. Outbound images are restricted to explicit marketplace hosts, resolved to public addresses and fetched through a pinned HTTPS connection; redirects are rejected and a streaming byte ceiling applies before accumulating the complete image. Cache administration defaults to denial without a separate credential. Controlled tests cover these boundaries, not live marketplace compatibility or a deployed proxy's access rules. Those deployment checks remain a separate release gate.

Showing the interface honestly

The product page imports the extension's renderer, styles, currency helpers, and theme engine. Its interactive demos use deterministic sample listings and simulated state transitions. They do not query live marketplaces or measure matching accuracy. The store link is the route to the installable extension. Firefox build support is distinct from a verified Firefox store release.

Price history has a separate limit: ordered historical prices do not include an exact timestamp for every change. The chart labels interpolated dates as estimates. The same principle applies to matching: confidence and usable fallbacks are implemented behavior; relevance gains and time saved still need a separate, representative evaluation.