| Camera is not opening | Permission blocked, insecure origin, device camera busy or unsupported browser. | Use HTTPS, review permissions and close competing camera apps, or switch to image upload. |
| Camera displays a black preview | Camera is covered, disabled or unavailable to the browser. | Check device permissions, select another camera and reload. |
| QR is visible but not decoded | Glare, blur, low contrast or cropped quiet zone. | Retake a sharper image with the full border visible. |
| Screenshot paste does nothing | Clipboard does not contain image content or browser access is restricted. | Copy the screenshot again or save it and use Upload. |
| Uploaded file is not recognized | File may be damaged or have an unsupported encoding. | Convert it to PNG or JPG and retry. |
| QR image is too small | Too few pixels for reliable module sampling. | Use the original high-resolution image instead of a heavily compressed thumbnail. |
| Black-and-white inverted code fails | Unusual colors can confuse the detector. | Upload a clear version or try improved contrast and a normal color arrangement. |
| Multiple codes produce unexpected results | Several symbols are present in the image or PDF. | Inspect each listed result and match it to its source position. |
| Non-QR barcode cannot be scanned | Selected browser lacks native BarcodeDetector support for its symbology. | Try a compatible browser/device or a dedicated supported barcode reader. |
| PDF scan is slow | Large multipage rendering and image decoding can be computationally expensive. | Process a shorter document or extract the relevant page for testing. |
| PDF contains an unreadable QR | Embedded code may be too tiny, damaged or rasterized at low quality. | Use a sharper original source and inspect the PDF at higher resolution. |
| Decoded URL seems wrong | Code may contain a redirect or a different printed link than its caption claims. | Verify full decoded URL against an independent trusted source. |
| QR security scan says safe but site looks suspicious | Heuristic signals did not identify the deception. | Do not enter credentials; confirm the domain by navigating through an official site. |
| URL is flagged as suspicious | Shortener, look-alike domain, raw IP or dangerous URL scheme detected. | Avoid opening it until an independent verification establishes legitimacy. |
| UPI payee does not match store | Payment sticker could be incorrect or tampered with. | Do not pay; ask the merchant to confirm the correct payee in a trusted channel. |
| UPI amount is missing | Payment code leaves amount optional. | Enter and verify the amount in your payment app before authorizing. |
| WiFi QR reveals a password unexpectedly | Typical WiFi QR structures store the password in readable form. | Avoid sharing the QR or its decoded text and rotate the password if exposed. |
| Contact has missing fields | QR vCard syntax may be incomplete or nonstandard. | Inspect raw payload and correct the imported contact manually. |
| Authenticator QR includes a secret | otpauth content contains a live TOTP seed. | Disable history and avoid exports or screenshots; safeguard or rotate compromised secrets. |
| History disappears | Browser data was cleared or private mode did not persist records. | Use a controlled export only when retention is authorized. |
| History retains sensitive content | History feature can save decoded data to browser storage. | Delete entries, clear history or enable privacy mode. |
| CSV export displays malformed characters | Spreadsheet importer may use unexpected encoding. | Open as UTF-8 and inspect contents rather than altering the raw value. |
| JSON output differs from raw text | Automatic content classification may normalize fields. | Use the raw payload when exact bytes or syntax matter. |
| Camera torch button missing | Device or browser does not expose torch capability. | Use better ambient light; do not assume flashlight control exists on every device. |
| Scan pauses or lags | High resolution camera frames, large images or other tabs use resources. | Close heavy tasks, try a static screenshot or reduce source size without losing code clarity. |
| External link prompts unexpected action | QR content can encode app schemes or sensitive operations. | Do not approve the action without independently confirming intent. |
| Developer API request fails | Endpoint, authorization, request shape or availability may differ. | Verify current API documentation and test with non-sensitive sample data. |
| Barcode returns only a number | Retail barcodes often store identifiers rather than product descriptions. | Use an authorized product catalog to interpret the identifier. |