Pre-parse transformations sanitize raw query strings before parsing key-value pairs to close HTTP parameter pollution and evade parsing discrepancies. These can be chained with post-parse transformations in a single rule statement, enhancing request normalization.
New transformations include standard encoding and trimming functions plus specialized decodings developed by AWS security researchers. Each transformation uses 10 WCUs and is available in all AWS regions without extra charge beyond standard WAF pricing.
Source & further reading
AWS WAF adds pre-parse text transformations and new text transformations ↗Source published 2026-07-29. This report was prepared with AI assistance from the linked primary-source material. Claims and limitations should be checked against the original announcement or research.