diff --git a/README.md b/README.md
index bf4c5c4..0adc33b 100644
--- a/README.md
+++ b/README.md
@@ -12,3 +12,9 @@ GET http://localhost:4567/api/1/preview/:label.pdf
 POST http://localhost:4567/api/1/print/:label
 
 where :label is a `spejstore` label.id or item.short_id
+
+to test without spejstore running locally, pass:
+
+```sh
+DEBUG_JSON='{"short_id":"abcdef","name":"Some long test item","owner":"testowner"}' bundle exec ruby main.rb
+```
diff --git a/main.rb b/main.rb
index d2dd13a..2d913db 100644
--- a/main.rb
+++ b/main.rb
@@ -41,7 +41,11 @@ BACKEND_URL = 'https://inventory.hackerspace.pl/api/1/'
 CODE_PREFIX = "https://inventory.hackerspace.pl/"
 
 def api(uri)
-  Excon.get(BACKEND_URL + uri + "/").json!
+  if ENV["DEBUG_JSON"]
+    JSON.parse(ENV["DEBUG_JSON"])
+  else
+    Excon.get(BACKEND_URL + uri + "/").json!
+  end
 end
 
 def render_identicode(data, id, extent)