How to Test If SeaText AI Is Causing Cross-Origin Issues in Your Multi-Domain SPA
To isolate whether SeaText AI triggers CORS errors, temporarily remove or disable the SeaText snippet, reload your SPA across all domains, and verify that the cross-origin errors stop. Then re-enable the snippet and inspect...
Quick isolation test
Open your SPA in a browser where the CORS error appears. Comment out or remove the SeaText AI snippet from your index.html or framework entry point. Reload every domain your SPA touches. If the cross-origin errors disappear, SeaText is the likely source. If they persist, the problem lies elsewhere.
Step-by-step diagnostic sequence
- Capture the baseline error. Open DevTools (F12), go to the Console tab, and note the exact CORS message — including the blocked URL and the origin that tried to access it.
- Disable SeaText. Remove the
<script async src="...seatext...">line from your HTML, or set a feature flag that prevents the snippet from loading. Rebuild and redeploy if your build process inlines the snippet. - Reload all affected domains. Visit each domain and subdomain your SPA uses. Clear cache or open an incognito window to avoid stale service workers.
- Check the Console again. The original CORS error should be gone. If a different CORS error remains, it belongs to another script or API call.
- Re-enable SeaText and inspect Network. Restore the snippet. Reload and switch to the Network tab. Filter for "seatext" or the SeaText CDN domain. Look for red (failed) requests with a CORS status or a blocked-by-response header.
- Correlate timestamps. Match the failed SeaText request time to the CORS error timestamp in the Console. A match confirms SeaText as the culprit.
Why cross-origin issues appear in multi-domain SPAs
SeaText loads its script asynchronously from a CDN domain (e.g., cdn.seatext.com). When your SPA runs on app.example.com and also serves content from shop.example.com or blog.example.org, the browser treats each unique scheme/host/port tuple as a separate origin. If the SeaText script or any XHR/fetch it initiates lacks the proper Access-Control-Allow-Origin header for one of those origins, the browser blocks the response and logs a CORS error.
The SeaText documentation explicitly flags this: "If your SPA interacts with multiple domains, ensure that the SEATEXT AI script is compatible and does not face cross-origin issues." The snippet uses async loading and writes an ID to localStorage, both of which are origin-scoped. A script loaded on app.example.com cannot read localStorage written on shop.example.com, which can cause secondary failures that look like CORS problems.
This matters because multi-domain SPAs often share authentication state, user preferences, or shopping carts across subdomains. When a third-party script like SeaText cannot access the same storage or make cross-origin requests, features break silently. Users see missing translations, broken personalization, or failed A/B tests without obvious error messages.
Common misdiagnoses
- Third-party analytics or chat widgets often load from their own CDNs and generate CORS errors that appear alongside SeaText.
- API calls from your own backend missing
Access-Control-Allow-Originfor a subdomain. - Service worker caching an old version of the SeaText script after you've updated the snippet URL.
- Browser extensions that inject scripts and trigger cross-origin violations.
Run the isolation test above before blaming SeaText. If the error vanishes only when SeaText is disabled, you have a true positive.
Verifying the fix
After you adjust the SeaText configuration (see the next section), repeat the diagnostic sequence. The Network tab should show a successful 200 OK for the SeaText script with an Access-Control-Allow-Origin: * or your specific origin in the response headers. The Console should remain free of CORS messages related to the SeaText domain.
Also verify that SeaText functionality works: translations appear, personalization triggers, and A/B test variants load. Check the SeaText dashboard for incoming events from each domain. If events arrive from all domains, the CORS issue is resolved.
Configuration adjustments that resolve most cases
- Serve the SeaText script from your own domain. Proxy
cdn.seatext.comthrough a path on each SPA domain (e.g.,/seatext/seatext.js) so the script becomes same-origin. - Ensure the CDN returns
Access-Control-Allow-Origin: *. Contact SeaText support if the header is missing or restricted. - Avoid sharing
localStorageacross origins. If you need a shared visitor ID, store it in a cookie withDomain=.example.com; SameSite=None; Secureor use a backend endpoint that all subdomains call. - Load the snippet once per top-level navigation. In React/Vue/Angular routers, place the snippet in
index.htmlrather than a component that remounts on route change.
Each adjustment addresses a specific failure mode. Proxying the script eliminates cross-origin requests entirely. Adding the CORS header lets the browser accept the response. Shared cookies replace origin-scoped localStorage. Single-load placement prevents duplicate initialization that can race with navigation.
Key facts
| Fact | Detail | Source |
|---|---|---|
| SeaText snippet loading | Async script tag; writes an ID to localStorage | S1 |
| Cross-origin warning in docs | "If your SPA interacts with multiple domains, ensure that the SEATEXT AI script is compatible and does not face cross-origin issues." | S1 |
| SPA integration entry points | index.html or main JS/TS file where framework mounts | S1 |
| Verification step in docs | Build, serve, open DevTools, check Console and Network tabs | S1 |
| Supported frameworks | React, Vue, Angular (generic SPA instructions) | S1 |
Limitations of this test
- Only confirms whether SeaText is the source of the observed CORS error. Other silent cross-origin failures (e.g., blocked fonts, iframes) won't appear.
- Does not prove SeaText is misconfigured — your CDN proxy or cookie policy may be the root cause.
- Assumes you can deploy a snippet-free build to a staging or production environment. If you cannot, use a browser extension (e.g., Requestly) to block the SeaText script URL at runtime.
- Cannot detect intermittent CORS failures that depend on timing, cache state, or specific user agents.
- Does not validate SeaText's post-load API calls (e.g., to
api.seatext.com) which may have separate CORS requirements.
Practical scenarios
Scenario 1: Subdomain translation fails
Your main app at app.example.com loads SeaText. The shop at shop.example.com loads the same snippet. Translations work on the app but not the shop. Console shows CORS error for cdn.seatext.com from shop.example.com. The CDN returns Access-Control-Allow-Origin: https://app.example.com only. Fix: ask SeaText to add shop.example.com or return *.
Scenario 2: localStorage ID mismatch
SeaText writes a visitor ID to localStorage on app.example.com. The shop on shop.example.com reads localStorage and gets null. Personalization fails. No CORS error appears. Fix: move the ID to a shared cookie or backend session.
Scenario 3: Service worker serves stale script
You updated the SeaText snippet URL. Users with the old service worker still fetch the old script from cache. CORS errors appear because the old script URL is gone. Fix: unregister service worker or version the script URL.
Decision criteria for fixes
| Approach | When to choose | Trade-off |
|---|---|---|
| Proxy script via your domain | You control infrastructure; want zero CORS risk | Added maintenance; must keep script updated |
| Request CORS header from SeaText | Quick fix; no infrastructure changes | Depends on vendor response time |
| Shared cookie for visitor ID | Need cross-domain identity; already use cookies | Requires Secure + SameSite=None; GDPR considerations |
| Backend endpoint for shared state | Complex identity needs; already have API layer | Added latency; more code to maintain |
FAQ
What if the CORS error mentions a different domain than SeaText?
That error comes from another script or API. Run the same isolation test against each third-party script until you find the offender.
Can I keep SeaText on one domain and disable it on others?
Yes. Include the snippet only in the index.html of domains that need it. SeaText's dashboard lets you scope agents per domain.
Does SeaText make XHR/fetch calls after the initial script load?
The documentation does not detail post-load network behavior. If you see subsequent calls to api.seatext.com or similar, those also need CORS headers.
Will a service worker cache the SeaText script and hide my fix?
Yes. Unregister the service worker (Application → Service Workers → Unregister) or bump the script URL with a query string (?v=2) to force a fresh fetch.
What headers should the SeaText CDN return?
At minimum Access-Control-Allow-Origin: * or your exact origin. Access-Control-Allow-Methods: GET and Access-Control-Allow-Headers: Content-Type are typical for script loads.
Can I self-host the SeaText script?
SeaText does not publish a self-hosting option in the public docs. Contact support if you need to proxy or mirror the script on your own infrastructure.
How do I know which origin the browser sends in the Origin header?
Open DevTools Network tab, click the failed SeaText request, check Request Headers. The Origin header shows the exact scheme/host/port the browser uses.
What if SeaText works on localhost but fails on staging?
Localhost often uses a single origin. Staging may use multiple subdomains. The CDN may allow localhost but not your staging domains. Check the CORS header on each environment.
When to contact SeaText support
If the isolation test confirms SeaText as the source, you've verified the CDN lacks the required CORS headers, and you cannot proxy the script yourself, open a support ticket with the exact error message, the affected origins, and the Network tab screenshot showing the failed request and response headers.
Further reading and comparison sources
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Further reading and comparison sources
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