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Templates and fields

Templates contain HTML, CSS, a page size, sample values, and a field schema. Rendering runs without external network access.

Built-in placeholders

Common fields include name, course, date, and score. CertKit injects cert_id and the QR code; callers cannot override them.

Custom fields

Define a lowercase field key, label, type, and required state. API and CSV values are plain strings with a 500-character limit. Unknown, missing, or oversized fields fail validation before a certificate is issued.

Safe assets

Use uploaded workspace assets. Remote images, scripts, frames, and external CSS are rejected so rendering remains deterministic and isolated.

Publishing

Preview before publishing. Publishing creates an immutable version. Later edits create another version and never alter already-issued certificates.