chore: naming custom domain

[livio-a]

Which Problems Are Solved

As part of the consistent naming effort, this PR focuses on "Custom Domains".

How the Problems Are Solved

• All terms referring to a domain identifying an instance were changed to "Custom Domain" or "custom domain".
• All placeholders were changed to ${CUSTOM_DOMAIN} or $CUSTOM_DOMAIN (if escaping was not possible)
• Some other placeholders were change to the same style.
• One occurrence of custom domain was changed to organization domain to prevent misunderstandings.

Additional Changes

None

Additional Context

• closes Naming consistency — Custom Domain #11296
• customer portal is fixed on https://github.com/zitadel/website/pull/1570
• angular example is updated on chore: naming custom domain zitadel-angular#29

[vercel]

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Project	Deployment	Review	Updated (UTC)
docs	Ready	Preview, Comment	Jan 19, 2026 7:12am
zitadel-login	Ready	Preview, Comment	Jan 19, 2026 7:12am

[github-actions]

Thanks for your contribution @livio-a! 🎉

Please make sure you tick the following checkboxes before marking this Pull Request (PR) as ready for review:

• I have reviewed my changes and would approve it
• Documentations and examples are up-to-date
• Logical behavior changes are tested automatically
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• My code has no repetitions
• The PR title adheres to the conventional commit format
• The example texts in the PR description are replaced.
• If there are any open TODOs or follow-ups, they are described in issues and link to this PR
• If there are deviations from a user stories acceptance criteria or design, they are agreed upon with the PO and documented.

[nx-cloud]

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☁️ Nx Cloud last updated this comment at 2026-01-19 07:24:56 UTC

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 43.14%. Comparing base (4c078c1) to head (3f3ff95).
⚠️ Report is 196 commits behind head on main.

❗ There is a different number of reports uploaded between BASE (4c078c1) and HEAD (3f3ff95). Click for more details.

HEAD has 2 uploads less than BASE

Flag	BASE (4c078c1)	HEAD (3f3ff95)
core-unit-tests	1	0
core-integration-tests-postgres	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #11383       +/-   ##
===========================================
- Coverage   65.66%   43.14%   -22.53%     
===========================================
  Files        1832     1973      +141     
  Lines      168248   164641     -3607     
===========================================
- Hits       110480    71028    -39452     
- Misses      52292    89700    +37408     
+ Partials     5476     3913     -1563     

Flag	Coverage Δ
api-test-integration	0.00% <ø> (?)
api-test-unit	44.21% <ø> (?)
core-integration-tests-postgres	?
core-unit-tests	?

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[Copilot]

Pull request overview

This pull request standardizes the naming convention for "Custom Domain" terminology throughout the ZITADEL codebase. The changes focus on:

Changes:

• Standardizing placeholder format from $CUSTOM-DOMAIN (with hyphen) to $CUSTOM_DOMAIN (with underscore) across all protobuf service definitions
• Capitalizing "Custom Domain" consistently in documentation and comments to match the proper feature name
• Updating shell variable placeholders to use the ${CUSTOM_DOMAIN} format for consistency
• Clarifying distinction between "Custom Domain" (instance-level) and "organization domain" (organization-level) in one location

Reviewed changes

Copilot reviewed 105 out of 105 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
proto/zitadel/webkey/v2beta/webkey_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/webkey/v2/webkey_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/user/v2beta/user_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/user/v2/user_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/system.proto	Updated placeholder and capitalized "Custom Domains" in comments
proto/zitadel/settings/v2beta/settings_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/settings/v2/settings_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/settings/v2/domain_settings.proto	Capitalized "Custom Domain" in comment
proto/zitadel/session/v2beta/session_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/session/v2/session_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/saml/v2/saml_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/resources/userschema/v3alpha/user_schema_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/resources/user/v3alpha/user_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/resources/debug_events/v3alpha/debug_events_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/project/v2beta/project_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/org/v2beta/org_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/org/v2/org_service.proto	Updated placeholder and changed "custom domains" to "organization domains" for clarity
proto/zitadel/oidc/v2beta/oidc_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/oidc/v2/oidc_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/management.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN and $YOUR-ORGANIZATION to $YOUR_ORGANIZATION
proto/zitadel/internal_permission/v2beta/internal_permission_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/instance/v2beta/instance_service.proto	Updated placeholder and capitalized "Custom Domain" in comments
proto/zitadel/instance/v2/instance_service.proto	Capitalized "Custom Domain" consistently throughout
proto/zitadel/instance/v2/instance.proto	Capitalized "Custom Domain" in comments
proto/zitadel/idp/v2/idp_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/group/v2/group_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/feature/v2beta/feature_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/feature/v2/feature_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/auth.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/app/v2beta/app_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/analytics/v2beta/telemetry.proto	Capitalized "Custom Domains" in comment
proto/zitadel/admin.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/action/v2beta/action_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
proto/zitadel/action/v2/action_service.proto	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN
internal/static/i18n/en.yaml	Capitalized "Custom Domain" in error message
docs/src/components/environment.jsx	Capitalized "Custom Domain" in UI label
docs/sidebars.js	Capitalized "Custom Domains" in API description
docs/docs/support/troubleshooting.mdx	Capitalized "Custom Domain" in documentation
docs/docs/self-hosting/manage/custom-domain.md	Capitalized "Custom Domain" in documentation
docs/docs/self-hosting/manage/cache.md	Capitalized "Custom Domains" in documentation
docs/docs/self-hosting/deploy/troubleshooting/_instance_not_found.mdx	Capitalized "Custom Domain" throughout
docs/docs/guides/solution-scenarios/restrict-console.mdx	Updated placeholder format and improved placeholder documentation
docs/docs/guides/solution-scenarios/domain-discovery.mdx	Capitalized "Custom Domain" throughout
docs/docs/guides/solution-scenarios/b2c.mdx	Changed heading from "Custom domain" to "Organization Domain" for clarity
Multiple migration/integration guide files	Standardized placeholder format from $CUSTOM-DOMAIN to ${CUSTOM_DOMAIN}
Multiple API example files	Updated placeholder format consistently
docs/base.yaml	Updated placeholder from $CUSTOM-DOMAIN to $CUSTOM_DOMAIN

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