Custom-built websites decay silently through dependency drift, framework end-of-life, Core Web Vitals regression, API rot, CMS schema drift, and accessibility gaps. Unlike managed platforms, custom stacks require active ownership across seven distinct maintenance layers: security, dependencies, performance, content/CMS, accessibility, infrastructure, and SEO. A practical checklist organized by cadence (CI, weekly, monthly, quarterly, annual) is outlined, along with what a proper SLA should include. Monthly maintenance costs range from $500–$2,500 for small marketing sites to $8,000+ for complex apps. Tools like Dependabot, Renovate, Snyk, and Lighthouse CI are recommended for automation. The European Accessibility Act has been enforceable since June 2025, making WCAG 2.2 AA compliance a legal requirement for EU-facing products. A hybrid in-house/retainer model is recommended for most teams.
