diff --git a/core/src/main/scala/codesearch/core/util/RegexTester.scala b/core/src/main/scala/codesearch/core/util/RegexTester.scala
new file mode 100644
index 0000000..1d10d24
--- /dev/null
+++ b/core/src/main/scala/codesearch/core/util/RegexTester.scala
@@ -0,0 +1,16 @@
+package codesearch.core.util
+
+import scala.util.matching.Regex
+
+object RegexTester {
+
+  def regexIsInvalid(regex: String, line: String): Boolean = {
+    try {
+      regex.r.findAllMatchIn(line)
+      false
+    } catch {
+      case x: java.util.regex.PatternSyntaxException => true
+    }
+  }
+
+}
diff --git a/web-server/app/views/resultFrame.scala.html b/web-server/app/views/resultFrame.scala.html
index 2e9de4d..8c7dab1 100644
--- a/web-server/app/views/resultFrame.scala.html
+++ b/web-server/app/views/resultFrame.scala.html
@@ -8,21 +8,38 @@
 @import codesearch.web.SnippetHelper
 
 @import java.net.URLEncoder
+@import codesearch.core.util.RegexTester
 @(
         lang: String,
         insensitive: Boolean,
         space: Boolean,
-        precise: Boolean,
         query: String,
         updated: String,
         packages: Seq[PackageResult],
-        totalMatches: Int
+        totalMatches: Int,
+        precise: Boolean,
+        sources: Boolean,
+        withoutTests: Boolean,
 )
 
 @regex = @{
     RegexConstructor(query = query, space = space, insensitive = insensitive, precise = precise)
 }
 
+@if(RegexTester.regexIsInvalid(regex, "line")) {
+    <script>
+        if (!document.getElementsByClassName('error')[0].classList.contains('show')) {
+            document.getElementsByClassName('error')[0].classList.add('show')
+            inpQuery.classList.add('error')
+        }
+    </script>
+}
+@if(!RegexTester.regexIsInvalid(regex, "line")) {
+    <script>
+            document.getElementsByClassName('error')[0].classList.remove('show')
+        inpQuery.classList.remove('error')
+    </script>
+}
 <section class="container">
     <span class="text-secondary">Index updated @updated</span> <br>
 
@@ -71,4 +88,4 @@ <h4 class="display-7" style="margin-bottom: 0em; margin-top: 2em; text-align: le
             </pre>
         }
     }
-</section>
+</section>
\ No newline at end of file
diff --git a/web-server/app/views/searchBox.scala.html b/web-server/app/views/searchBox.scala.html
index e6b8cfa..28237f5 100644
--- a/web-server/app/views/searchBox.scala.html
+++ b/web-server/app/views/searchBox.scala.html
@@ -8,12 +8,14 @@
         precise: Boolean,
         sources: Boolean,
         withoutTests: Boolean,
+        invalidRegex: Boolean = false
 )
 
 <section class="container-fluid">
     <div class="col-lg-6 mx-auto p-3 h7 justify-content-center" style="position: relative;">
         <form>
             <section class="warning warning-query">Please provide a string to search for.</section>
+            <section class="error warning-query">You entered wrong regexp.</section>
             <div class="input-group mb-2">
                 <input type="text" class="form-control" name="query" value="@query" class="query">
                 <div class="input-group-append">
diff --git a/web-server/app/views/searchResults.scala.html b/web-server/app/views/searchResults.scala.html
index 09b385d..94f878c 100644
--- a/web-server/app/views/searchResults.scala.html
+++ b/web-server/app/views/searchResults.scala.html
@@ -25,6 +25,6 @@
 
     @wrapper(s"Codesearch | $lang", headExtra) {
         @searchBox(s"/$lang/search", query, filter, filePath, insensitive, space, precise, sources, withoutTests)
-        @resultFrame(lang, insensitive, space, precise, query, updated, packages, totalMatches)
+        @resultFrame(lang, insensitive, space, query, updated, packages, totalMatches, precise, sources, withoutTests)
         @pagination(page, totalMatches, callURI)
     }