QR labels and scanning

A QR label saves you the walk back to the laptop. Instead of finding a bottle in the freezer, remembering what it was, and then searching for it in Inventory, you point your phone at the sticker and the item is already on screen with its actions ready. Working from the bench rather than the desk is part of the point.

What the code on a container is

Every label carries a short code: a string of letters and numbers that Labsistant issues and that points at one specific thing in your lab. The code is the whole label. The QR square is just a convenient way for a camera to read it, which is why you can also type the code by hand when a sticker is scratched or frosted over.

A few things follow from that:

• One live label per item. Asking for a label again gives you back the one that already exists rather than a second one. A single container cannot end up with two live codes on two different stickers.
• The code is not the item's name. It carries no reagent name, lot number, or quantity. When you are online, a scan reads the current record from Labsistant, so a label printed months ago can still show the current quantity. Offline results are cached snapshots, as explained below.
• A label can be revoked. A revoked label stays readable but stops opening anything, which is what you want when a container is decontaminated and reused.

Codes exist for inventory items, storage locations, and scheduled experiments. Today the button that makes one lives on inventory items.

Make a label and put it on the container

Labels are made on the web app, not on the phone.

1. Open Inventory and click the item to open its detail panel.
2. Scroll to QR Label.
3. Click Generate QR label. The short code and its QR square appear, along with a version number. If this item already has a live label, you get that same one back rather than a new one.
4. Click Print label to print this one label on its own: the QR square, which holds the web link, with the short code underneath. If your lab prints labels from its own label-printer software, click Download PNG or Download SVG instead to save the square as an image.
5. The two links behind the code sit under the square, if you need one on its own:
   • Copy web link gives you a link that opens the item.
   • Copy app link gives you a link that opens straight into the Labsistant app on a phone.

For inventory items, the label controls are available to the lab PI, the item's manager or owner, a member of its owning group, or anyone for shared lab stock. Closed items cannot generate or revoke labels.

To retire a label, click Revoke label and confirm. It stops opening the item; generate a new label to replace it. Revoking a label does not delete the inventory item.

Two habits worth keeping:

• Keep the short code as text underneath the square. Print label does this for you; if you lay out the label yourself from a downloaded image, add the code under it. Cameras struggle with frost, condensation, and curved 1.5 mL tubes. A readable code underneath means the label still works when the square does not.
• Put the label where it survives. Cap tops get wiped, and a label on the bottom of a box faces the shelf. The side of a container, above the fill line, is usually the one spot that stays both clean and visible.

If you are labelling a freezer, a shelf, or a box rather than a container, read Create a storage location and Grid boxes and slots first, so the thing you are labelling exists in Labsistant before you stick anything on it.

Scan it on your phone

The phone controls below use the English labels currently shown in the mobile app.

1. Open the Labsistant app and go to Scan.
2. The camera opens automatically once permission is granted. The first time, allow camera access on your phone. If you have switched the camera off, tap Camera. If permission was denied, use Open settings to enable it or enter the code by hand.
3. Hold the square in frame. The lookup starts automatically; there is no shutter button. Use the zoom buttons or pinch to zoom, and Torch if you need more light.
4. If the camera cannot read the square, type the short code into the QR code field and tap Look up. That is the same lookup, and it is often faster than fighting with a reflection.

Once the label opens, the item appears with what you can do to it from where you are standing. What those actions mean, and which to reach for, is covered in Update, consume, or adjust an item's quantity.

Rapid repeated scans of the same label are ignored to prevent duplicate lookups. Scanning alone does not change inventory: confirm the action shown on screen, or choose Scan next to read another label.

When offline, the app can look up a label cached on this device. Any displayed item data is an earlier snapshot, not a live quantity. Inventory changes stay unavailable until you are online and the server has confirmed the current item.

When a scan finds nothing

A scan that comes back empty is usually telling you something specific rather than failing at random. Match the message:

Take QR code not found seriously, because it deliberately covers both an unknown code and a target you cannot access. First check that the printed code belongs to the container you are actually holding. If the sticker is wrong or the label has been retired, ask someone with label access to generate the correct label and replace the sticker. A known revoked label can also show the separate revoked message above.

An inaccessible target gets the same QR code not found wording rather than revealing that a code exists. This is deliberate: holding a sticker must not reveal another lab's records. If a colleague can open the same label and you cannot, check lab membership and item access with your PI. A failed lookup alone is not proof that the label needs replacing.