diff --git a/docs/build/schema.md b/docs/build/schema.md
index 6f0cca7..aa969ce 100644
--- a/docs/build/schema.md
+++ b/docs/build/schema.md
@@ -546,6 +546,7 @@ Key | Required | Type | Description
 `dict` | no | `boolean` | Is this field a key/value input?
 `computed` | no | `boolean` | Is this field automatically populated (and hidden from the user)?
 `altersDynamicFields` | no | `boolean` | Does the value of this field affect the definitions of other fields in the set?
+`inputFormat` | no | `string` | Useful when you expect the input to be part of a longer string. Put "{{input}}" in place of the user's input (IE: "https://{{input}}.yourdomain.com").
 
 -----
 
diff --git a/exported-schema.json b/exported-schema.json
index 112955d..29092f5 100644
--- a/exported-schema.json
+++ b/exported-schema.json
@@ -150,6 +150,11 @@
         "altersDynamicFields": {
           "description": "Does the value of this field affect the definitions of other fields in the set?",
           "type": "boolean"
+        },
+        "inputFormat": {
+          "description": "Useful when you expect the input to be part of a longer string. Put \"{{input}}\" in place of the user's input (IE: \"https://{{input}}.yourdomain.com\").",
+          "type": "string",
+          "pattern": "^.*{{input}}.*$"
         }
       },
       "additionalProperties": false
diff --git a/lib/schemas/FieldSchema.js b/lib/schemas/FieldSchema.js
index e5d2f8e..f106ed4 100644
--- a/lib/schemas/FieldSchema.js
+++ b/lib/schemas/FieldSchema.js
@@ -101,6 +101,12 @@ module.exports = makeSchema({
       description: 'Does the value of this field affect the definitions of other fields in the set?',
       type: 'boolean',
     },
+    inputFormat: {
+      description: 'Useful when you expect the input to be part of a longer string. Put "{{input}}" in place of the user\'s input (IE: "https://{{input}}.yourdomain.com").',
+      type: 'string',
+      // TODO: Check if it contains one and ONLY ONE '{{input}}'
+      pattern: '^.*\{\{input\}\}.*$'
+    },
   },
   additionalProperties: false,
 }, [
diff --git a/test/index.js b/test/index.js
index c46815c..28f600e 100644
--- a/test/index.js
+++ b/test/index.js
@@ -129,6 +129,50 @@ describe('app', () => {
       results.errors[1].stack.should.eql('instance.searchOrCreates.fooSearchOrCreate.search must match a "key" from a search (options: fooSearch)');
       results.errors[2].stack.should.eql('instance.searchOrCreates.fooSearchOrCreate.create must match a "key" from a create (options: fooCreate)');
     });
+
+    it('should validate inputFormat', () => {
+      const appCopy = copy(appDefinition);
+      appCopy.authentication = {
+        type: 'custom',
+        test: {
+          url: 'https://example.com',
+        },
+        fields: [
+          {
+            key: 'subdomain',
+            type: 'string',
+            required: true,
+            inputFormat: 'https://{{input}}.example.com',
+          },
+        ],
+      };
+      const results = schema.validateAppDefinition(appCopy);
+      results.errors.should.eql([]);
+    });
+
+    it('should invalidate illegal inputFormat', () => {
+      const appCopy = copy(appDefinition);
+      appCopy.authentication = {
+        type: 'custom',
+        test: {
+          url: 'https://example.com',
+        },
+        fields: [
+          {
+            key: 'subdomain',
+            type: 'string',
+            required: true,
+            inputFormat: 'https://{{input}.example.com',
+          },
+        ],
+      };
+      const results = schema.validateAppDefinition(appCopy);
+      results.errors.length.should.eql(1);
+
+      const error = results.errors[0];
+      error.name.should.eql('pattern');
+      error.instance.should.eql('https://{{input}.example.com');
+    });
   });
 
   describe('export', () => {