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Action Tags Hidden and Readonly

@HIDDEN & @READONLY — Visibility Control

Article ID RC-AT-02 — @HIDDEN & @READONLY — Visibility Control
Domain Action Tags
Applies To All REDCap project types; requires Project Design and Setup rights
Prerequisite RC-AT-01 — Action Tags: Overview
Version 1.0
Last Updated 2026
Author See KB-SOURCE-ATTESTATION.md
Related Topics RC-AT-01 — Action Tags: Overview; RC-AT-03 — Radio & Dropdown Action Tags; RC-FD-02 — Online Designer; RC-BL-01 — Branching Logic: Overview & Scope

1. Overview

This article covers the most commonly used action tags: @HIDDEN and @READONLY, along with their situational variants. These tags control field visibility and editability across different REDCap contexts.

2. @HIDDEN — Hiding Fields

@HIDDEN hides a field from view. The field and its data still exist in the project; users simply cannot see or interact with it.

Important: @HIDDEN overrides branching logic. A field tagged with @HIDDEN is always hidden, regardless of any branching logic conditions.

Common uses:

  • Preserving deprecated fields without deleting historical data
  • Hiding calculated fields so users cannot see intermediate values
  • Creating honeypot fields in surveys to detect automated bot submissions

2.1 Situational Variants

Tag Where it hides
@HIDDEN Everywhere (form, survey, Mobile App, PDFs)
@HIDDEN-SURVEY Only when accessed as a survey
@HIDDEN-FORM Only when accessed as a data entry form
@HIDDEN-APP Only in the REDCap Mobile App
@HIDDEN-PDF Only in PDF exports (the only way to exclude from PDFs)

2.2 Combining Variants

Multiple variants can be combined. For example, to hide a field in surveys and in the Mobile App:

@HIDDEN-SURVEY @HIDDEN-APP

3. @READONLY — Making Fields Non-Editable

@READONLY displays a field normally but prevents any changes to its value. Read-only fields appear slightly greyed out.

Common uses:

  • Displaying pre-loaded contact information that staff can review but not edit
  • Showing calculated or piped values for reference without allowing modification

3.1 Situational Variants

Tag Where it's read-only
@READONLY Everywhere (form, survey, Mobile App)
@READONLY-SURVEY Only in surveys
@READONLY-FORM Only in data entry forms
@READONLY-APP Only in the REDCap Mobile App

3.2 Combining Variants

Multiple read-only variants can be combined:

@READONLY-FORM @READONLY-APP

4. Combining @HIDDEN and @READONLY

These two tag families can be mixed to achieve fine-grained control. For example, to show a field as read-only to staff but hide it from surveys and exclude it from PDFs:

@READONLY-FORM @HIDDEN-SURVEY @HIDDEN-PDF

Caution: Using a bare @HIDDEN tag alongside @READONLY-FORM will override the read-only behavior — the field will be hidden from staff entirely. Always use specific variants to achieve your intended effect.

5. Common Questions

Q: Does @HIDDEN prevent the field's data from appearing in reports or exports?

A: No. @HIDDEN only hides the field in the data entry and survey interface. Data still appears in reports, the Codebook, and data exports. Use user rights and export settings to restrict data access.

Q: What happens if I use @HIDDEN on a field that also has branching logic?

A: The @HIDDEN tag always wins. The field will be hidden regardless of the branching logic conditions. This is by design — @HIDDEN provides absolute hiding.

Q: Can I temporarily disable @HIDDEN without removing it?

A: Yes. Use the Quick-Modify Field(s) bulk editor to Deactivate the tag, then Reactivate it later. This is useful during instrument testing.

6. Common Mistakes

Using @HIDDEN when you meant @HIDDEN-PDF. The bare @HIDDEN tag does not exclude a field from PDFs. You must use @HIDDEN-PDF specifically.

Mixing bare @HIDDEN with @READONLY variants. A bare @HIDDEN overrides all read-only variants on the same field. Use specific variants (@HIDDEN-FORM, etc.) instead.

Adding @READONLY to a field expecting users to enter data and assuming the field will still appear on surveys. @READONLY displays the field but prevents editing. If you meant to hide it from one context but keep it editable elsewhere, use context-specific variants like @READONLY-FORM and @HIDDEN-SURVEY instead of applying a bare @READONLY to all contexts.

Marking a field as required and @HIDDEN-SURVEY and expecting it to be enforced during survey completion. REDCap only enforces the required flag in the context where the field is visible. A field with both required = 'y' and @HIDDEN-SURVEY will not prompt the survey respondent to fill it in — the required constraint is effectively inactive during survey completion. This matters in hybrid forms that serve as both a survey (for initial collection) and a data entry form (for ongoing staff management). Fields that must be completed by staff in data entry mode, but should be invisible to survey respondents, should be marked required — but be aware that records created through the survey will have those fields blank until staff fill them in.