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A field binding is a placeholder you write inside a Destination URL that QRtub replaces with real data at the moment someone scans. It is what lets one URL template serve every Item in a Collection instead of one URL per Item.
Scan the code on Item “EXC-203”, whose serial number is SN-2024-203, and the browser opens:
The same template on a different Item substitutes that Item’s serial number, so every code routes to its own pre-filled URL from one configuration.

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Syntax rules

Write a namespace, a dot, and a field name, wrapped in double curly braces.
  • Double braces are required. {item.name} is not a binding. Single braces are sent to the browser literally, so the receiving system gets the characters {item.name} instead of a value.
  • The namespace prefix is required. {{name}} does not resolve; write {{item.name}}.
  • Field names are case-sensitive. {{item.Status}} does not resolve. {{item.status}} does.
  • Spaces inside the braces are ignored. {{ item.name }} behaves identically to {{item.name}}.
  • You can use as many bindings as you like in one URL, mixed freely with literal text: https://cmms.example.com/wo/new?asset={{item.item_number}}&site={{item.location}}.
The same field names go into a condition without the braces — item.status == "operational". Braces build a value; a bare reference tests one.

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The namespaces

Eight namespaces exist. Each one is only readable where the data behind it exists, which is why the last three are not available everywhere.

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Values are inserted exactly as stored

There is no automatic URL encoding. Whatever is in the field is dropped into the URL character for character. A field value containing a space, an ampersand, a question mark or a slash will produce a URL that the receiving system reads differently from what you intended — an & in a value, for example, looks to the receiving system like the start of a new query parameter. Either confirm the receiving system tolerates those characters, or keep bound fields to plain identifiers — serial numbers, asset numbers, Item IDs — which is what most templates use anyway.

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What happens when a field is empty

This differs depending on where the binding sits, and the difference matters. In a Destination URL, an empty or missing field invalidates the whole URL. QRtub will not open a half-built link. If any binding in the template resolves to nothing, that Destination is treated as unresolved: a conditional rule is skipped and the next rule is tried, and a plain Destination URL resolves to nothing at all, which lands the scan on the “this link isn’t ready yet” screen instead of a broken URL. The same rule applies to a binding that resolves to a list or a nested object rather than a single value — {{item.tags}} is an array, so a URL containing it never resolves. In a Page section, an empty field renders as an empty string and most sections then hide themselves rather than display a blank. The exception is the ActionLink section, which checks its own href first and hides itself entirely if a binding there cannot be resolved. Neither case produces an error message. A Destination that quietly never fires is almost always a binding that never resolved, so check the field name’s spelling and case first, and then check that the Item you are testing with actually has a value in that field.

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Session fields

session describes the signed-in team member looking at a Page, and is empty for an ordinary anonymous scan. There are two usable values, session.user.id and session.user.email, plus the session.user object itself, which is what the common test uses:
That expression is true only for a signed-in member of your team, which is how the AdminToolbar section keeps owner-only shortcuts off the version of the Page the public sees. session is not part of the data available when a Direct-Mode scan resolves a Destination, so it cannot be used to route a redirect.

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Renaming a field does not break a binding

If you rename a custom field on a Collection, QRtub rewrites the Destination URLs, fallback URLs and conditions that referenced the old name, in place, when you save. Page template bindings are stored against a hidden stable identifier and never see the rename at all.