diff --git a/components/ace-editor.vue b/components/ace-editor.vue
index 47553b7d..b348126c 100644
--- a/components/ace-editor.vue
+++ b/components/ace-editor.vue
@@ -21,8 +21,10 @@
 <script>
 const DEFAULT_THEME = "twilight"
 
-import ace from "ace-builds"
-import "ace-builds/webpack-resolver"
+import ace from "ace-builds";
+import "ace-builds/webpack-resolver";
+import jsonParse from '../functions/jsonParse';
+import debounce from '../functions/utils/debounce';
 
 export default {
   props: {
@@ -55,8 +57,10 @@ export default {
   watch: {
     value(value) {
       if (value !== this.cacheValue) {
-        this.editor.session.setValue(value, 1)
-        this.cacheValue = value
+        this.editor.session.setValue(value, 1);
+        this.cacheValue = value;
+
+        this.provideLinting(value);
       }
     },
     theme() {
@@ -94,10 +98,13 @@ export default {
     this.cacheValue = this.value
 
     editor.on("change", () => {
-      const content = editor.getValue()
-      this.$emit("input", content)
-      this.cacheValue = content
-    })
+      const content = editor.getValue();
+      this.$emit("input", content);
+      this.cacheValue = content;
+      this.provideLinting(content);
+    });
+
+    this.provideLinting(this.value);
   },
 
   methods: {
@@ -105,8 +112,29 @@ export default {
       if (this.theme) {
         return this.theme
       }
-      return this.$store.state.postwoman.settings.THEME_ACE_EDITOR || DEFAULT_THEME
+      return (
+        this.$store.state.postwoman.settings.THEME_ACE_EDITOR || DEFAULT_THEME
+      );
     },
+
+    provideLinting: debounce(function (code) {
+      if (this.lang === "json") {
+        try {
+          jsonParse(code);
+          this.editor.session.setAnnotations([]);
+        } catch (e) {
+          const pos = this.editor.session.getDocument().indexToPosition(e.start, 0);
+          this.editor.session.setAnnotations([
+            {
+              row: pos.row,
+              column: pos.column,
+              text: e.message,
+              type: "error"
+            }
+          ]);
+        }
+      }
+    }, 2000)
   },
 
   destroyed() {
diff --git a/functions/jsonParse.js b/functions/jsonParse.js
new file mode 100644
index 00000000..3ccfb055
--- /dev/null
+++ b/functions/jsonParse.js
@@ -0,0 +1,310 @@
+/**
+ *  Copyright (c) 2019 GraphQL Contributors
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+/**
+ * This JSON parser simply walks the input, generating an AST. Use this in lieu
+ * of JSON.parse if you need character offset parse errors and an AST parse tree
+ * with location information.
+ *
+ * If an error is encountered, a SyntaxError will be thrown, with properties:
+ *
+ *   - message: string
+ *   - start: int - the start inclusive offset of the syntax error
+ *   - end: int - the end exclusive offset of the syntax error
+ *
+ */
+export default function jsonParse(str) {
+  string = str;
+  strLen = str.length;
+  start = end = lastEnd = -1;
+  ch();
+  lex();
+  const ast = parseObj();
+  expect('EOF');
+  return ast;
+}
+
+let string;
+let strLen;
+let start;
+let end;
+let lastEnd;
+let code;
+let kind;
+
+function parseObj() {
+  const nodeStart = start;
+  const members = [];
+  expect('{');
+  if (!skip('}')) {
+    do {
+      members.push(parseMember());
+    } while (skip(','));
+    expect('}');
+  }
+  return {
+    kind: 'Object',
+    start: nodeStart,
+    end: lastEnd,
+    members,
+  };
+}
+
+function parseMember() {
+  const nodeStart = start;
+  const key = kind === 'String' ? curToken() : null;
+  expect('String');
+  expect(':');
+  const value = parseVal();
+  return {
+    kind: 'Member',
+    start: nodeStart,
+    end: lastEnd,
+    key,
+    value,
+  };
+}
+
+function parseArr() {
+  const nodeStart = start;
+  const values = [];
+  expect('[');
+  if (!skip(']')) {
+    do {
+      values.push(parseVal());
+    } while (skip(','));
+    expect(']');
+  }
+  return {
+    kind: 'Array',
+    start: nodeStart,
+    end: lastEnd,
+    values,
+  };
+}
+
+function parseVal() {
+  switch (kind) {
+    case '[':
+      return parseArr();
+    case '{':
+      return parseObj();
+    case 'String':
+    case 'Number':
+    case 'Boolean':
+    case 'Null':
+      const token = curToken();
+      lex();
+      return token;
+  }
+  return expect('Value');
+}
+
+function curToken() {
+  return { kind, start, end, value: JSON.parse(string.slice(start, end)) };
+}
+
+function expect(str) {
+  if (kind === str) {
+    lex();
+    return;
+  }
+
+  let found;
+  if (kind === 'EOF') {
+    found = '[end of file]';
+  } else if (end - start > 1) {
+    found = '`' + string.slice(start, end) + '`';
+  } else {
+    const match = string.slice(start).match(/^.+?\b/);
+    found = '`' + (match ? match[0] : string[start]) + '`';
+  }
+
+  throw syntaxError(`Expected ${str} but found ${found}.`);
+}
+
+function syntaxError(message) {
+  return { message, start, end };
+}
+
+function skip(k) {
+  if (kind === k) {
+    lex();
+    return true;
+  }
+}
+
+function ch() {
+  if (end < strLen) {
+    end++;
+    code = end === strLen ? 0 : string.charCodeAt(end);
+  }
+}
+
+function lex() {
+  lastEnd = end;
+
+  while (code === 9 || code === 10 || code === 13 || code === 32) {
+    ch();
+  }
+
+  if (code === 0) {
+    kind = 'EOF';
+    return;
+  }
+
+  start = end;
+
+  switch (code) {
+    // "
+    case 34:
+      kind = 'String';
+      return readString();
+    // -, 0-9
+    case 45:
+    case 48:
+    case 49:
+    case 50:
+    case 51:
+    case 52:
+    case 53:
+    case 54:
+    case 55:
+    case 56:
+    case 57:
+      kind = 'Number';
+      return readNumber();
+    // f
+    case 102:
+      if (string.slice(start, start + 5) !== 'false') {
+        break;
+      }
+      end += 4;
+      ch();
+
+      kind = 'Boolean';
+      return;
+    // n
+    case 110:
+      if (string.slice(start, start + 4) !== 'null') {
+        break;
+      }
+      end += 3;
+      ch();
+
+      kind = 'Null';
+      return;
+    // t
+    case 116:
+      if (string.slice(start, start + 4) !== 'true') {
+        break;
+      }
+      end += 3;
+      ch();
+
+      kind = 'Boolean';
+      return;
+  }
+
+  kind = string[start];
+  ch();
+}
+
+function readString() {
+  ch();
+  while (code !== 34 && code > 31) {
+    if (code === 92) {
+      // \
+      ch();
+      switch (code) {
+        case 34: // "
+        case 47: // /
+        case 92: // \
+        case 98: // b
+        case 102: // f
+        case 110: // n
+        case 114: // r
+        case 116: // t
+          ch();
+          break;
+        case 117: // u
+          ch();
+          readHex();
+          readHex();
+          readHex();
+          readHex();
+          break;
+        default:
+          throw syntaxError('Bad character escape sequence.');
+      }
+    } else if (end === strLen) {
+      throw syntaxError('Unterminated string.');
+    } else {
+      ch();
+    }
+  }
+
+  if (code === 34) {
+    ch();
+    return;
+  }
+
+  throw syntaxError('Unterminated string.');
+}
+
+function readHex() {
+  if (
+    (code >= 48 && code <= 57) || // 0-9
+    (code >= 65 && code <= 70) || // A-F
+    (code >= 97 && code <= 102) // a-f
+  ) {
+    return ch();
+  }
+  throw syntaxError('Expected hexadecimal digit.');
+}
+
+function readNumber() {
+  if (code === 45) {
+    // -
+    ch();
+  }
+
+  if (code === 48) {
+    // 0
+    ch();
+  } else {
+    readDigits();
+  }
+
+  if (code === 46) {
+    // .
+    ch();
+    readDigits();
+  }
+
+  if (code === 69 || code === 101) {
+    // E e
+    ch();
+    if (code === 43 || code === 45) {
+      // + -
+      ch();
+    }
+    readDigits();
+  }
+}
+
+function readDigits() {
+  if (code < 48 || code > 57) {
+    // 0 - 9
+    throw syntaxError('Expected decimal digit.');
+  }
+  do {
+    ch();
+  } while (code >= 48 && code <= 57); // 0 - 9
+}