ERR_FIELD_MAPPING on Make.com: Field mapping error. Root cause: Source and target fields have incompatible data types Step 1: Identify the exact field type mismatch in the module. Open the failing Make.com scenario and click the module that shows the error. In the module configuration panel, look at the field that is receiving data — Make.com displays the expected type in grey text below the field label (e.g., "Number", "Date", "Boolean"). Compare this to the data type being mapped from the previous module. The most common mismatches are: text being sent to a Number field, a date string in the wrong format being sent to a Date field, and a comma-separated list being sent to a field that expects a single value. Step 2: Use a Set Variable or Tools module to convert the data type. Between the source module and the destination module, add a Make.com Tools → Set Variable module (or a Text Aggregator for list-to-text conversions). For number conversions, use the built-in parseNumber() function: in the variable value field, type parseNumber({{source_field}}) — this converts a text string like "42.5" to the number 42.5. For date conversions, use formatDate({{date_field}}, "YYYY-MM-DD") to standardise the format before it reaches the destination field. Step 3: Handle boolean fields explicitly. Boolean fields (true/false checkboxes) are a frequent source of type errors because APIs often return "true", "1", "yes", or "on" for the same logical value. Make.com does not automatically normalise these. In your Set Variable module, use an if() expression: if({{source_field}} = "true"; true; false). This converts any truthy string to a proper boolean before it reaches the destination. Test this with both a "true" and "false" value from your source to confirm both paths work. Step 4: Test the mapping with real data using the Run Once button. After adding your type conversion, click the "Run Once" button (play icon with a single dot) in the scenario editor. Make.com will execute the scenario once using the most recent real data from your trigger. Watch the data flow through each module — click each module bubble after the run to inspect the input and output bundles. Confirm the converted field now shows the correct type (a number without quotes, a date in ISO format, etc.) before the data reaches the destination module. Step 5: Add an error handler to catch future type failures gracefully. Right-click the destination module and select "Add error handler". Choose the "Resume" directive if you want the scenario to continue processing other records even when one record fails the type check. In the error handler branch, add a Make.com Email module or a Slack notification to alert you when a type mismatch occurs, including the bundle number and the raw value that failed. This prevents silent data loss when edge-case values slip through your conversion logic. Step 6: Document the field mapping in the scenario description. Once the fix is working, click the scenario name at the top of the editor and add a description noting which fields required type conversion and why. Include the conversion formula used. Make.com scenarios are often maintained by multiple people, and undocumented type conversions are frequently "fixed" by well-meaning colleagues who then reintroduce the original bug. A one-paragraph description prevents this.