Every variable Studio accepts inside a composition URL pattern, grouped by category. Studio's URL editor validates patterns against this set, typos and unknown variables are rejected before save.

Where each category is available:

{{entry.<field>}}: any field declared on the content type connected to the template.

URL pattern: /blogs/{{entry.title}}
Resolves to: /blogs/AI%20101                (entry.title = "AI 101")

Spaces are URL-encoded as %20. Studio's URL editor validates that <field> exists on the connected content type's schema; typos produce a field_not_exists validation error.

{{entry.<reference>.<field>}}: a field on an entry referenced by the current entry.

URL pattern: /authors/{{entry.primary_author.handle}}/posts/{{entry.title}}

primary_author must be a Reference field on the connected content type, and handle must exist on the referenced content type's schema.

For multi-reference fields (reference_to.length > 1), the sub-field is accepted if it exists on at least one of the referenced content types. The first match wins at resolve time.

References are auto-included in the SDK's useCompositionData fetch; you don't need to declare extendQuery.includeReferences for fields used in URL patterns.

Properties present on every CMA entry but not declared in the content type's schema. Allowed in patterns without a schema lookup:

{{taxonomy:<taxonomy_uid>}}: the value of a taxonomy assigned to the entry.

URL pattern: /{{taxonomy:industry}}/{{entry.title}}
Resolves to: /finance/quarterly-report       (entry has taxonomy industry = "finance")

Studio collects taxonomies referenced in patterns but doesn't validate the <taxonomy_uid> against the schema; taxonomy terms aren't part of the content type schema.

Five built-in metadata variables resolved from the request / project context, not from the entry. Available in both linked and Freeform patterns.

In the Edit URL modal:

• Linked templates show Insert chips for {{environment}}, {{entry.title}}, {{entry.uid}}, {{taxonomy:brand}}, {{locale}} (the chip exists, but prefer routing-layer locale + the SDK locale query option instead of inserting it)
• Freeform pages show only {{composition_uid}}

The chips are quick-insert shortcuts. The full set above is typeable manually: {{branch}}, {{content_type_uid}} and other entry / taxonomy variants work the same.

When you configure a content type's URL pattern (/blogs/:year/:month/:title), Studio auto-generates these pseudo variables from the matching pattern:

You can't type these by hand in the URL editor; pasting {{entry_created_date:year}} produces a pseudo_variable_not_allowed validation error. They're an internal marker the URL engine uses; the content type's :year-style pattern is the user-facing surface.

If you want a year in your URL without using the content type's URL pattern, store the year as an entry field and use {{entry.published_year}} instead.

*: matches exactly one path segment, captures it for routing alignment, carries no value.

URL pattern: /blogs/*
Matches:     /blogs/ai-101, /blogs/llm-economics, /blogs/agent-design

Used by legacy linked patterns from before variable-based URLs landed. The Edit URL modal warns when it detects a legacy pattern with a "This composition has a legacy URL pattern. Once changed, you cannot revert it." banner.

One-way migration. Confirming the change in the Edit URL modal upgrades the composition to a variable-based URL permanently; there is no rollback. Be sure the new pattern resolves correctly against your CT's fields before saving.

For new templates, prefer variable-based patterns (/blogs/{{entry.title}}); they carry data into the resolved URL instead of just routing it.

Pick a SLUG field, not the title. {{entry.title}} renders the display-name verbatim: "AI 101" → /blogs/AI%20101, which is fragile (capitals, spaces, %20-encoding, breaks on title rename). Bind the URL to your CT's slug field (commonly entry.url or entry.slug); Studio gives you /blogs/ai-101. The CT's url field is the canonical Contentstack URL slug; use it for the URL pattern, use {{entry.title}} for display only.

For a new linked template, Studio derives the URL pattern from the first available source (verified against composable-studio/src/iframe-url/createCompositionEntryUrl.ts:24-31 and its implementation at lines 113-126):

1. Custom Preview URL for the content type: strongly recommended; configure this once per CT. tryCustomPreviewUrl() runs first.
2. Content type URL pattern (e.g. /blogs/:title): tryContentTypeUrlPattern() runs if #1 returned null.
3. Default fallback: /<content_type_uid>/<composition_uid>/{{entry.title}}, createDefaultLinkedUrl() runs if #2 also returned null.

For Sections (always render in canvas, no visitor URL) and Freeform (no connected CT) the derivation skips #1+#2 and uses the default pattern directly.

Two extra source values exist in the SDK enum (COMPOSITION_PREVIEW_URL_SOURCES in composable-studio-sdk/packages/studio-client/src/url-metadata/types.ts:12) but apply OUTSIDE this derivation flow: - USER_SPECIFIED_PATTERN: the author hand-edited the URL via the URL pattern editor AFTER creation - LEGACY_URL: the composition pre-dates the URL-source metadata and runs on the legacy URL path

Dev configures once; authors never touch URLs. Set the Custom Preview URL on each content type when the CT is created (Content Models → CT → Settings → Custom Preview URL → e.g. /blogs/{{entry.url}} for blogs, /products/{{entry.slug}} for products). After that, every new linked template against that CT auto-derives the correct URL pattern; authors never edit URLs in Studio. Hand-editing a template's URL pattern is a smell that something upstream wasn't configured.

For Freeform, the default is /<content_type_uid>/<composition_uid>: CT UID and composition UID inlined as literal segments (identity-based, no entry).

See Templates: Connected content type for the derivation flow.

Studio's URL editor blocks save on any of these:

• Spaces in variable values are URL-encoded as %20
• Reference variables trigger an includeReferences query addition automatically; you don't need to declare it via extendQuery
• Taxonomy variables resolve from the entry's taxonomies.<uid> array; first value wins for multi-value taxonomies

• Templates: Connected content type: URL derivation order
• Freeform templates: what variables Freeform supports
• Install the Studio SDK: Fetch a composition: the extendQuery option