Topic Name
A publisher sends one concrete Topic Name. It cannot contain + or # wildcards.
MQTT Topic Designer Workbench
Design MQTT Topic Names and Topic Filters, then test whether the broker will route messages as intended.
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Learner-ready MQTT topic designer workbench with topic namespace linting, Topic Name versus Topic Filter separation, wildcard matching, $ topic behavior, scale projection, scenario presets, source links, and local desktop/mobile visual verification.
MQTT Topic Designer Workbench
MQTT does not create folders on the broker. A Topic Name is a UTF-8 string used by a PUBLISH packet, and a Topic Filter is the subscription rule the broker compares against it. Use this workbench to design a namespace, test wildcard filters, and see the operational risk before deploying a fleet.
Diagnosis
A scoped telemetry hierarchy is ready for wildcard testing.
Topic name
Valid publish template
Filter result
Matches selected samples
Scale
720 possible topics
Topic Filter
A subscriber registers a Topic Filter. It may use + for one level and # for the final subtree.
String Matching
The broker routes by comparing each publish Topic Name with active filters. Topic case and every slash matter.
Namespace Choice
Good early levels let clients subscribe by tenant, site, device, data type, or event without overly broad filters.
Build hierarchy
Separate stable levels from variable identifiers.
Generate topics
Turn the template into concrete publish Topic Names.
Lint design
Find invalid syntax and maintainability risks.
Test filter
Check which sample messages a subscriber receives.
Estimate scale
Review topic count and filter scope.
Build hierarchy
The publish template is split into levels. Variable levels are placeholders that become concrete Topic Names before PUBLISH.
Publish to Subscribe
Publisher PUBLISH
v1/acme/factory-a/boiler-01/telemetry/temperature
Concrete Topic Name. Wildcards are not allowed here.
Subscriber filter
v1/acme/+/+/telemetry/temperature
The broker compares the Topic Name to this Topic Filter.
Which messages arrive?
Scoped designGood
The namespace has useful routing levels and the filter is narrow enough for a telemetry dashboard.
Syntax and design checks
Broker reasoning
Valid
The generated publish topics contain no wildcards.
Valid
The wildcard placement is valid for a Topic Filter.
3 of 6
Only the intended tenant and metric arrive.
720
Estimated concrete topics from the selected fleet size.
120
Estimated matching topics for this subscription.
PUBLISH uses a concrete name
No + or #. A template can show variables for teaching, but the actual packet carries a filled-in string.
SUBSCRIBE uses a matching rule
+ matches one complete level. # matches the remaining subtree and must be the final level.
System namespace is special
A filter that starts with # or + does not match Topic Names that start with $.
Put routing intent in levels
Tenant, site, device, and data category levels make authorization and dashboards easier than flat strings.
Technical notes and primary sources
Topic Names and Filters
MQTT defines Topic Names for PUBLISH and Topic Filters for SUBSCRIBE. Wildcards belong to Topic Filters, not Topic Names.
Full-level matching
+ and # must occupy a whole level. # must be either the entire filter or the final level after a slash.
Topics are not storage folders
The broker matches strings. Hierarchies are conventions that help humans, ACLs, dashboards, and subscriptions behave predictably.
Practice prompts
Tenant dashboard
Design a filter that sees all telemetry for one tenant but not commands or status updates.
Device command panel
Change the namespace so a maintenance tool can subscribe to commands for one site without receiving every site.
Presence monitor
Use a status topic and decide whether your filter should include all devices, one site, or one device.