Snap rejected every event with a silent 400 — Arabic URLs were malformed

The situation

A luxury beauty brand in the UAE had implemented Snap Conversions API to improve signal coverage after seeing strong Snap performance in Gulf markets. Despite the implementation, Snap Events Manager showed low event match rates and the account rep confirmed events weren't being received consistently.

The problem

The brand's website used Arabic-language URL paths (e.g., /منتجات/عطور). These Arabic characters in the page_url field of the Snap CAPI payload were not being URL-encoded before transmission. Snap's API was rejecting these events with 400 errors silently — no visible error in the dashboard, just missing events. The implementation worked perfectly for English URL paths.

What we did

1. Pulled Snap CAPI server logs — 400 responses appearing on all events from Arabic-path product pages
2. Identified root cause: page_url containing unencoded Arabic characters in JSON payload
3. Applied URL encoding (encodeURIComponent) to the page_url field before passing to CAPI endpoint
4. Tested across all Arabic-path pages — all events now returning 200 responses
5. Added monitoring alert for any CAPI 400 response rate exceeding 1%

Why it worked

Snap's CAPI endpoint expects standard URL encoding for all string fields. Arabic, Hebrew, and other non-Latin character sets in URL paths must be percent-encoded before inclusion in the JSON payload. This is a non-obvious requirement that isn't prominently documented and only affects brands with non-Latin URL structures — but it silently kills 100% of events from those pages.