From npm Package to Hosted API: When to Upgrade

local checker vs Hosted API — feature comparison

When the npm package is enough

The local checker works well when you need a quick compliance pass on a small number of pre-translated German listings — verifying a handful of SKUs before uploading, running a Git pre-commit hook on already-localized copy, or checking an exported spreadsheet offline.

Because it exits with code 1 on any violation, it fits natively into local build steps without requiring an API key or network access.

npx listloco-checker listing.json

When the Hosted API adds value

Scenario 1 — batch processing 50+ listings

Running batch processing across a full catalogue means processing hundreds of SKUs in sequence or in parallel. The Hosted API tracks usage per key, handles concurrent requests without lock contention, and returns structured JSON you can pipe directly into your build pipeline or database. The npm package supports batch loops too, but concurrency management is on you.

Scenario 2 — end-to-end localization in CI

If your CI pipeline needs to translate English product copy into compliant German in a single step, the POST /localize endpoint handles translation and compliance gating in one call. The example below is copy-paste-ready for any CI runner (GitHub Actions, GitLab CI, Jenkins, Bitbucket Pipelines, etc.).

curl -s -X POST "https://listloco.p.rapidapi.com/localize" \
  -H "Content-Type: application/json" \
  -H "X-RapidAPI-Key: <YOUR_RAPIDAPI_KEY>" \
  -H "X-RapidAPI-Host: listloco.p.rapidapi.com" \
  --data '{
    "marketplace": "amazon",
    "sourceLang": "en",
    "targetLang": "de",
    "listing": {
      "title": "Ergonomic Office Chair Model EC-400 Mesh Back, Black",
      "brand": "Ergonox",
      "material": "Mesh",
      "size": "One Size",
      "color": "black",
      "quantity": 1
    }
  }'

Scenario 3 — back-translation divergence check

The back-translation divergence gate is only available in the Hosted API. After translating en→de, the API round-trips the German output back to English and compares it to the original using a Jaccard lexical score. If the divergence exceeds the threshold or any hard-fact token (model number, numeral, unit) is absent from the round-trip, the gate fails.

This catches cases where a model number like EC-400 silently mutates during translation — a small lexical change that represents a complete product-identity break. The npm local checker does not perform this round-trip check.

The back-translation divergence gate is one additional risk indicator, not a complete compliance check. It does not cover all of Amazon DE's content policies, and no automated tool can account for every possible marketplace ruling.

Scenario 4 — team workflow with a shared API key

When multiple developers or microservices need compliance checks, a shared RapidAPI key provides a single usage dashboard and shared quota pool. Each team member does not need a local Node.js install; any language or runtime that can make an HTTPS request works.

Try it without a key first

The free Amazon DE Listing Checker runs the same banned-word, title-length, required-attribute, and preservation gates entirely in your browser — no signup, no API key, nothing sent to a server. A good first step before committing to the Hosted API.

Ready to upgrade? Start with the free plan

The free RapidAPI plan includes 100 listings per month with no credit card required. Paid plans unlock higher monthly quotas and lower per-listing overage rates.

View pricing → · Getting started guide →