How to Fix WhatsApp Number Format Errors: E.164 Standard, Common Mistakes, and Multi-Country List Normalization Order

Most WhatsApp number format errors occur because numbers are not written in full international format: missing country code, leftover leading 0 or 00/011, mixed symbols, or not encoded according to special rules for Argentina and Mexico. This article provides standard formats for each scenario, a comparison of common mistakes, and the processing order for multi-country lists from cleaning and deduplication to per-country validation.