diff --git a/frontend.go b/frontend.go
index 5c694af..2d77045 100644
--- a/frontend.go
+++ b/frontend.go
@@ -112,6 +112,19 @@ func resultPage(w http.ResponseWriter, r *http.Request) {
       Secret: secret,
     }
 
+    // set the repo to opt-in
+    if strings.ToUpper(r.URL.Query().Get("optin")) == "ON" {
+      repo.OptIn = true
+    }
+    // define custom opt-in flag
+    if r.URL.Query().Get("optinFlag") != "" {
+      repo.OptInFlag = r.URL.Query().Get("optinFlag")
+    }
+    // define custom opt-out flag
+    if r.URL.Query().Get("optoutFlag") != "" {
+      repo.OptOutFlag = r.URL.Query().Get("optoutFlag")
+    }
+
     name := "web"
     hook := github.Hook{
       Name: &name, Events: []string{"pull_request"},
diff --git a/repo.go b/repo.go
index c7c2f85..911e73f 100644
--- a/repo.go
+++ b/repo.go
@@ -27,6 +27,9 @@ type Repo struct {
   Slug string
   Token string
   Secret string
+  OptIn bool
+  OptInFlag string `gorm:"default:'ci'"`
+  OptOutFlag string `gorm:"default:'ci skip'"`
 }
 
 type Repos []Repo
diff --git a/templates/auth.html b/templates/auth.html
index ba62653..27daf07 100644
--- a/templates/auth.html
+++ b/templates/auth.html
@@ -15,6 +15,29 @@
       <input type="text" class="form-control" id="repoInput" name="repo" aria-describedby="repoHelp" placeholder="Enter your project slug">
       <small id="repoHelp" class="form-text text-muted">Your project slug is the Github user- and repository name separated by a slash e.g. ganggo/federation</small>
     </div>
+    <div class="form-check mb-3">
+      <input type="checkbox" class="form-check-input" id="optinInput" name="optin" describedby="optinHelp">
+      <label class="form-check-label" for="optinInput">Check if you want to opt-in on a new test</label>
+      <small id="optinHelp" class="form-text text-muted">
+        That would mean that tests are triggered if you specify <code>[ci]</code> in the PR title, body, commit-message
+        or if the PR was tagged with <span class="badge badge-primary">ci</span>. If you leave the box unchecked
+        tests will be triggered on every pull-request. However you can skip them by using <code>[ci skip]</code>
+        in the mentioned fields or tag it with <span class="badge badge-primary">ci skip</span>.
+      </small>
+      <div class="form-group">
+        <label for="optinFlagInput">(optional) Custom Flags</label>
+        <input type="text" class="form-control" id="optinFlagInput" name="optinFlag" aria-describedby="optinFlagHelp" placeholder="default is 'ci'">
+        <small id="optinFlagHelp" class="form-text text-muted">
+          If you want to use custom build triggers for opt-in you can specify it here.
+        </small>
+      </div>
+      <div class="form-group">
+        <input type="text" class="form-control" name="optoutFlag" aria-describedby="optoutFlagHelp" placeholder="default is 'ci skip'">
+        <small id="optoutFlagHelp" class="form-text text-muted">
+          If you want to use custom build triggers for opt-out you can specify it here.
+        </small>
+      </div>
+    </div>
     <button type="submit" class="btn btn-primary">Submit</button>
   </form>
 </div>
diff --git a/webhook.go b/webhook.go
index a9bec60..31373f1 100644
--- a/webhook.go
+++ b/webhook.go
@@ -25,6 +25,8 @@ import (
   "encoding/json"
   "github.com/jinzhu/gorm"
   _ "github.com/jinzhu/gorm/dialects/sqlite"
+  "strings"
+  "context"
 )
 
 func webhook(w http.ResponseWriter, r *http.Request) {
@@ -54,16 +56,18 @@ func webhook(w http.ResponseWriter, r *http.Request) {
   }
 
   // skip all events except for open PRs
-  if *pr.State != "open" {
+  if pr.GetState() != "open" {
     logger.Println("Ignore closed pull request")
     fmt.Fprintf(w, `{}`)
     return
   }
 
   var repo Repo
-  err = db.Where("slug = ?", *pr.Base.Repo.FullName).Find(&repo).Error
+  err = db.Where("slug = ?",
+    pr.GetBase().GetRepo().GetFullName(),
+  ).Find(&repo).Error
   if err != nil {
-    logger.Println(err, *pr.Base.Repo.FullName)
+    logger.Println(err, pr.GetBase().GetRepo().GetFullName())
     fmt.Fprintf(w, `{"error":"repo not registered"}`)
     return
   }
@@ -76,24 +80,86 @@ func webhook(w http.ResponseWriter, r *http.Request) {
   //  return
   //}
 
+  var flagExists = false
+  var buildFlag = repo.OptOutFlag
+  if repo.OptIn {
+    buildFlag = repo.OptInFlag
+  }
+
+  // check PR title and body for [ci] or [ci skip] flag
+  if pr.Title != nil && strings.Contains(pr.GetTitle(),
+      fmt.Sprintf("[%s]", buildFlag)) {
+    flagExists = true
+  } else if pr.Body != nil && strings.Contains(pr.GetBody(),
+      fmt.Sprintf("[%s]", buildFlag)) {
+    flagExists = true
+  } else {
+    // check labels for build flag if we haven't already found it
+    for _, label := range pr.Labels {
+      if label.Name != nil && strings.Contains(label.GetName(), buildFlag) {
+        flagExists = true
+        break
+      }
+    }
+
+    if !flagExists {
+      // last but not least check the commit message for flags
+      client := github.NewClient(nil)
+      commits, _, err := client.PullRequests.ListCommits(
+        context.Background(),
+        pr.GetHead().GetUser().GetLogin(),
+        pr.GetHead().GetRepo().GetName(),
+        pr.GetNumber(), &github.ListOptions{})
+
+      if err == nil && len(commits) > 0 {
+        // check only last commit since older ones are irrelevant
+        commitMsg := commits[len(commits)-1].GetCommit().GetMessage()
+        flagExists = strings.Contains(
+          commitMsg, fmt.Sprintf("[%s]", buildFlag))
+      } else {
+        logger.Printf("Commits is empty or an error occurred: %+v\n", err)
+      }
+    }
+  }
+
+  // ignoring pull-request! Repository is set
+  // to opt-in and no build flag was found
+  if repo.OptIn && !flagExists {
+    logger.Printf(
+      "Ignore optin=%t buildFlag=%s flagExists=%t\n",
+      repo.OptIn, buildFlag, flagExists)
+    fmt.Fprintf(w, `{}`)
+    return
+  }
+
+  // ignoring pull-request! Repository is set
+  // to opt-out and a skip flag was found
+  if !repo.OptIn && flagExists {
+    logger.Printf(
+      "Ignore optin=%t buildFlag=%s flagExists=%t\n",
+      repo.OptIn, buildFlag, flagExists)
+    fmt.Fprintf(w, `{}`)
+    return
+  }
+
   build := Build{
     RepoID: repo.ID,
     Matrix: fmt.Sprintf(
       `"PROJECT=%s PRREPO=%s PRSHA=%s"`,
       repo.Project,
-      *pr.Head.Repo.CloneURL,
-      *pr.Head.SHA,
+      pr.GetHead().GetRepo().GetCloneURL(),
+      pr.GetHead().GetSHA(),
     ),
-    PRUser: *pr.Head.User.Login,
-    PRRepo: *pr.Head.Repo.Name,
-    PRSha: *pr.Head.SHA,
+    PRUser: pr.GetHead().GetUser().GetLogin(),
+    PRRepo: pr.GetHead().GetRepo().GetName(),
+    PRSha: pr.GetHead().GetSHA(),
   }
+
   err = db.Create(&build).Error
   if err != nil {
     logger.Println(err)
     fmt.Fprintf(w, `{"error":"database error"}`)
     return
   }
-
   fmt.Fprintf(w, `{}`)
 }