diff --git a/packages/builder/src/userInterface/propsDefinitionParsing/types.js b/packages/builder/src/userInterface/propsDefinitionParsing/types.js
index ee7232dada..43fceea17f 100644
--- a/packages/builder/src/userInterface/propsDefinitionParsing/types.js
+++ b/packages/builder/src/userInterface/propsDefinitionParsing/types.js
@@ -11,13 +11,29 @@ const defaultDef = typeName => () => ({
     required:false,
     default:types[typeName].default,
     options: typeName === "options" ? [] : undefined,
-    elementDefinition: typeName === "array" ? "string" : undefined
+    elementDefinition: typeName === "array" ? {} : undefined
 });
 
 const propType = (defaultValue, isOfType, defaultDefinition) => ({
     isOfType, default:defaultValue, defaultDefinition
 });
 
+/*export const expandPropDef = propDef => {
+    const p = isString(propDef)
+              ? types[propDef].defaultDefinition()
+              : propDef;
+    
+    if(!isString(propDef)) {
+        const def = types[propDef.type].defaultDefinition();
+        assign(propDef, def);
+    }
+
+    if(p.type === "array" && isString(p.elementDefinition)) {
+        p.elementDefinition = types[p.elementDefinition].defaultDefinition()
+    }
+    return p;
+}*/
+
 const isComponent = isObjectLike;
 
 export const types = {
@@ -26,5 +42,6 @@ export const types = {
     number: propType(() => 0, isNumber, defaultDef("number")),
     array: propType(() => [], isArray, defaultDef("array")),
     options: propType(() => "", isString, defaultDef("options")),
-    component: propType(() => ({_component:""}), isComponent, defaultDef("component"))
+    component: propType(() => ({_component:""}), isComponent, defaultDef("component")),
+    asset: propType(() => "", isString, defaultDef("asset")),
 };
\ No newline at end of file
diff --git a/packages/builder/src/userInterface/propsDefinitionParsing/validatePages.js b/packages/builder/src/userInterface/propsDefinitionParsing/validatePages.js
new file mode 100644
index 0000000000..7d48c58b6c
--- /dev/null
+++ b/packages/builder/src/userInterface/propsDefinitionParsing/validatePages.js
@@ -0,0 +1,66 @@
+import { recursivelyValidate } from "./validateProps";
+import { 
+    isString, 
+    keys, 
+    flatten,
+    isArray,
+    map,
+    filter
+} from "lodash/fp";
+import { common } from "budibase-core";
+const pipe = common.$;
+
+export const validatePage = (page, getComponent) => {
+    const errors = [];
+    const error = message => errors.push(message);
+
+    const noIndex = !page.index || !page.index._component;
+    if(noIndex) {
+        error("Must choose a component for your index.html");
+    }
+
+    if(!page.appBody 
+        || !isString(page.appBody) 
+        || !page.appBody.endsWith(".json")) {
+        error("App body must be set toa valid JSON file");
+    }
+
+    const indexHtmlErrors = noIndex 
+    ? []
+    : pipe(
+        recursivelyValidate(page.index, getComponent), [
+        map(e => `Index.html: ${e.error}`)
+    ]);
+
+    return [...errors, ...indexHtmlErrors];
+}
+
+export const validatePages = (pages, getComponent) => {
+
+    let errors = [];
+    const error = message => errors.push(message);
+
+    if(!pages.main) {
+        error("must have a 'main' page");
+    }
+
+    if(!pages.unauthenticated) {
+        error("must have a 'unauthenticated' (login) page");
+    }
+
+    if(!pages.componentLibraries 
+      || !isArray(pages.componentLibraries) 
+      || pages.componentLibraries.length === 0) {
+
+        error("componentLibraries must be set to a non-empty array of strings");
+    }
+
+    const pageErrors = pipe(pages, [
+        keys,
+        filter(k => k !== "componentLibraries"),
+        map(k => validatePage(pages[k], getComponent)),
+        flatten
+    ]);
+
+    return [...errors, ...pageErrors];
+}
\ No newline at end of file
diff --git a/packages/builder/src/userInterface/propsDefinitionParsing/validateProps.js b/packages/builder/src/userInterface/propsDefinitionParsing/validateProps.js
index 2078a5297b..dedfd17ca8 100644
--- a/packages/builder/src/userInterface/propsDefinitionParsing/validateProps.js
+++ b/packages/builder/src/userInterface/propsDefinitionParsing/validateProps.js
@@ -30,6 +30,13 @@ export const recursivelyValidate = (rootProps, getComponent, stack=[]) => {
         return getComponent(componentName);
     }
 
+    if(!rootProps._component) {
+        const errs = [];
+        makeError(errs, "_component", stack)("Component is not set");
+        return errs;
+        // this would break everything else anyway
+    }
+
     const propsDef = getComponentPropsDefinition(
         rootProps._component);
 
@@ -80,18 +87,26 @@ export const recursivelyValidate = (rootProps, getComponent, stack=[]) => {
     return flattenDeep([errors, ...childErrors, ...childArrayErrors]);
 }
 
-const expandPropDef = propDef =>
-    isString(propDef)
-    ? types[propDef].defaultDefinition()
-    : propDef;
+const expandPropDef = propDef => {
+    const p = isString(propDef)
+              ? types[propDef].defaultDefinition()
+              : propDef;
+    if(p.type === "array" && isString(p.elementDefinition)) {
+        p.elementDefinition = types[p.elementDefinition].defaultDefinition()
+    }
+    return p;
+}
 
 
 export const validateProps = (propsDefinition, props, stack=[], isFinal=true) => {
 
     const errors = [];
 
-    if(!props._component) 
+    if(!props._component) {
         makeError(errors, "_component", stack)("Component is not set");
+        return errors;
+        // this would break everything else anyway
+    }
 
     for(let propDefName in propsDefinition) {
         
diff --git a/packages/builder/tests/validatePages.spec.js b/packages/builder/tests/validatePages.spec.js
new file mode 100644
index 0000000000..3305a6bf01
--- /dev/null
+++ b/packages/builder/tests/validatePages.spec.js
@@ -0,0 +1,92 @@
+import { 
+    validatePages, 
+    validatePage 
+} from "../src/userInterface/propsDefinitionParsing/validatePages";
+
+const validPages = () => ({
+    "main" : {
+        "index" : {
+            "_component": "testIndexHtml",
+            "title": "My Cool App",
+            "customScripts": [
+                {"url": "MyCustomComponents.js"}
+            ]
+        },
+        "appBody" : "./main.app.json"
+    },
+    "unauthenticated" : {
+        "index" : {
+            "_component": "testIndexHtml",
+            "title": "My Cool App - Login",
+            "customScripts": [
+                {"url": "MyCustomComponents.js"}
+            ]
+        },
+        "appBody" : "./unauthenticated.app.json"
+    },
+    "componentLibraries": ["./myComponents"]
+});
+
+const getComponent = name => ({
+    testIndexHtml : {
+        title: "string",
+        customScripts: {
+            type:"array", 
+            elementDefinition: {
+                url: "string"
+            }
+        }
+    }
+}[name])
+
+describe("validate single page", () => {
+
+    it("should return no errors when page is valid", () => {
+        const errors = validatePage(
+            validPages().main, 
+            getComponent);
+        
+        expect(errors).toEqual([]);
+    });
+
+    it("should return error when index is not set, or set incorrectly", () => {
+        let page = validPages().main;
+        delete page.index;
+        expect(validatePage(page, getComponent).length).toEqual(1);
+
+        page.index = {title:"something"}; // no _component
+        const noComponent = validatePage(page, getComponent);
+        expect(noComponent.length).toEqual(1);
+
+    });
+
+    it("should return error when appBody is not set, or set incorrectly", () => {
+        let page = validPages().main;
+        delete page.appBody;
+        expect(validatePage(page, getComponent).length).toEqual(1);
+
+        page.appBody = true; // not a string
+        expect(validatePage(page, getComponent).length).toEqual(1);
+
+        page.appBody = "something.js"; // not a json
+        expect(validatePage(page, getComponent).length).toEqual(1);
+
+    });
+
+});
+
+describe("validate pages", () => {
+
+    it("should return no errors when pages are valid", () => {
+        const errors = validatePages(
+            validPages(), 
+            getComponent);
+        
+        expect(errors).toEqual([]);
+    });
+
+    it("should return error when index is not set, or set incorrectly", () => {
+
+    });
+
+});