The Web Sustainability Guidelines (WSG) implicitly rely on robust text matching for core functionality, including user search (Guideline 2.8) and machine processing of metadata/code (Guideline 3.5, 3.11). Failure to define global text matching rules can lead to unpredictable search results, validation errors, and poor user experience for non-English content.

• 2.8 Ensure that navigation and wayfinding are well-structured
• 3.5 Avoid redundancy and duplication in code
• 3.11 Structure metadata for machine readability
• 3.16 Use dependencies appropriately and ensure maintenance

Strengthening relevant sections (especially in Section 3: Web Development) to direct implementers to consider the following implications of global text matching would be useful:

1. Unicode Normalization for Identifiers and Syntax

• Problem: Two strings or identifiers (e.g., database keys, CSS class names) can appear identical but be composed of different Unicode character sequences (e.g., precomposed 'é' vs. 'e' + combining accent). Without defined Normalization rules (NFC, NFD, or none), systems will treat these as different strings, breaking logic and efficiency.
• Recommendation: Implementers should be aware that matching syntactic content and identifiers must account for Unicode Normalization if canonical equivalence is desired.
• Reference: W3C I18N Best Practices, Section 6.3: Working with Unicode Normalization

2. Case Folding for Search and Input

• Problem: User searches must often be case-insensitive. Simple ASCII case folding is insufficient for global scripts (e.g., the Turkish dotted and dotless 'I').
• Recommendation: User-facing text matching (like search and sorting) should use Unicode Full Case Folding for case-insensitive matching, while syntactic content (like code identifiers) should generally be case-sensitive by default.
• Reference: W3C I18N Best Practices, Section 6.4: Case folding

Addressing these points is crucial for building performant, sustainable web products that function correctly in all languages.