diff --git a/api/Dockerfile b/api/Dockerfile
index 15f0d67e..cce0f4fc 100644
--- a/api/Dockerfile
+++ b/api/Dockerfile
@@ -22,6 +22,9 @@ ENV HOME=/home/outdated
 
 ENV PYTHONUNBUFFERED=1
 ENV DJANGO_SETTINGS_MODULE outdated.settings
+
+# prevent git from asking for credentials on wrong urls
+ENV GIT_ASKPASS true
 ENV APP_HOME=/app
 
 COPY pyproject.toml poetry.lock $APP_HOME/
diff --git a/api/outdated/models.py b/api/outdated/models.py
index 61b369bb..34694642 100644
--- a/api/outdated/models.py
+++ b/api/outdated/models.py
@@ -15,7 +15,10 @@ class Meta:
 
 
 class RepositoryURLField(models.URLField):
-    default_validators = [validators.RepositoryURLValidator()]
+    default_validators = [
+        validators.RepositoryURLValidator(),
+        validators.validate_repo_exists,
+    ]
 
 
 class UniqueBooleanField(models.BooleanField):
diff --git a/api/outdated/outdated/models.py b/api/outdated/outdated/models.py
index 233f45c0..dd70df7c 100644
--- a/api/outdated/outdated/models.py
+++ b/api/outdated/outdated/models.py
@@ -1,6 +1,7 @@
 from datetime import date, timedelta
 from os.path import basename, dirname
 
+from django.core.exceptions import ValidationError
 from django.db import models
 from django.db.models.functions import Lower
 
@@ -93,9 +94,17 @@ def version(self):
         return f"{self.release_version.version}.{self.patch_version}"
 
 
+def repo_url_unique(value: str):
+    existing_urls = [p.clone_path for p in Project.objects.all()]
+    if Project(repo=value).clone_path in existing_urls:
+        raise ValidationError(
+            "Repository already exists.", params={"value": value}, code="unique"
+        )
+
+
 class Project(UUIDModel):
     name = models.CharField(max_length=100, db_index=True)
-    repo = RepositoryURLField(unique=True)
+    repo = RepositoryURLField(unique=True, validators=[repo_url_unique])
     versioned_dependencies = models.ManyToManyField(Version, blank=True)
 
     class Meta:
diff --git a/api/outdated/validators.py b/api/outdated/validators.py
index c450d11d..bac7446f 100644
--- a/api/outdated/validators.py
+++ b/api/outdated/validators.py
@@ -1,4 +1,6 @@
-from django.core.validators import RegexValidator
+from subprocess import run
+
+from django.core.validators import RegexValidator, ValidationError
 from django.utils.deconstruct import deconstructible
 
 
@@ -6,3 +8,10 @@
 class RepositoryURLValidator(RegexValidator):
     regex = r"(http[s]?)(://)([\w\.@\:/\-~]+)(\.git)"
     message = "Enter a valid http or https url to a git repository."
+
+
+def validate_repo_exists(value: str):
+    """Validate the existance of a remote git repository"""
+    result = run(["git", "ls-remote", value], capture_output=True)
+    if result.returncode != 0:
+        raise ValidationError("Repository does not exist.", params={"value": value})