Glossary and FAQ
The same terms are also explained inside the app: open the main menu (☰) and choose Printing terms.
| Term | Meaning |
|---|---|
| Alignment offset | A small shift, in millimeters, that moves printed content to correct a printer that feeds labels off-center. |
| Banner page | A page some print systems add before or after a job. ThermalPrint turns it off. |
| Auto-length | A label setting for continuous rolls: the printed length follows the content instead of a fixed height. |
| Batch | Printing many labels in one go, either from a queue of files or from a spreadsheet merged into a design. |
| Clipping | Content that would be cut off at the paper edge. ThermalPrint blocks printing when it happens. |
| Code 128, Code 39, EAN, UPC, ITF, Codabar | Linear barcode types. See the Barcode reference. |
| Confinement | The sandbox a Snap runs in, which limits what files and devices it can reach. |
| Copies | How many identical labels to print for each label. |
| CSV | A plain text table with values separated by commas (or semicolons or tabs). Spreadsheet programs export it. |
| CUPS | The Common UNIX Printing System: the standard Linux service that manages printers and print jobs. ThermalPrint prints through it. |
| Data Matrix | A small square 2D barcode, good for tiny labels. |
| Design | A label you created in the Label Designer, saved as a .thermalprint file. |
| DPI | Dots per inch: how many printed dots fit in an inch. Common thermal printers are 203 or 300 DPI. |
| Driver | The software that translates a print job into commands your printer understands. |
| FNC1 | A control character in GS1 barcodes. It marks the start of GS1 data and ends a variable-length field. |
| GS1, application identifier (AI) | The global standard for supply-chain barcodes. An AI is the number in brackets, such as (01) for a product number, that says what the value after it means. |
| GTIN | Global Trade Item Number: the number behind a product barcode such as EAN-13 or UPC-A. |
| Media | The paper (here, label) size the printer driver offers, such as 4 × 6 in. |
| Object | One item on a label: a text box, barcode, QR code, shape, or image. |
| Placeholder | A ${name} marker in a design that is replaced with a value when the label is drawn. |
| Portal | A desktop service that lets a sandboxed app open or save files you choose, such as the file chooser. |
| PPD | A file that describes a printer's features and paper sizes to CUPS. |
| Profile | The settings ThermalPrint remembers for one printer. |
| QR code | A square 2D barcode that can hold web addresses and text. |
| Quiet zone | The blank margin around a barcode that a scanner needs to find its edges. |
| Queue (print queue) | The list of labels waiting to print in Import & Convert. Also, a printer's name in CUPS. |
| Raw queue | A CUPS queue that passes data straight to the printer without a driver. Needed for raw ZPL. |
| Rotated printing | A Label Designer option: design a label on its side so wide content reads straight, and rotate it 90° when it prints so it fits the label stock as loaded. |
| Serial number | A counting number printed with ${serial}. |
| SSCC | Serial Shipping Container Code: an 18-digit number that identifies one pallet or parcel. |
| Thermal printer | A printer that makes marks with heat on special paper, so it needs no ink or toner. |
| Threshold | Turning every pixel fully black or white. It can harm thin barcode bars. |
| Processed folder | A subfolder named Processed inside the watch folder. When the matching option is on, printed labels are moved there. |
| Watch folder | A folder ThermalPrint checks for new label files to add to the queue. |
| ZPL | Zebra Programming Language: commands that some label printers understand directly. |
Frequently asked questions#
Does ThermalPrint work with my printer?#
If CUPS can print to it and its driver advertises your paper or label size, yes. ThermalPrint is designed for thermal label printers, but it works with regular laser and inkjet printers as well: choose A4 or Letter in Print Center, or use File → Print on a sheet… to put several labels on one page. Zebra, Rollo, Brother, ORGSTA, Dymo, Munbyn, Phomemo, and many other label printers work this way. Raw ZPL needs a printer that understands ZPL.
Can it print postage?#
No. ThermalPrint prepares and prints labels. It does not buy postage or create tracking numbers, and it does not connect to carrier or marketplace accounts.
Why does the preview differ from my printed label?#
The preview shows exactly what is sent. Differences come from the printer: its calibration, darkness, margins, or the loaded roll. Use the alignment test and print one label before a roll.
Is it free?#
Yes. ThermalPrint is open source under the MIT license, created by Alexis Rios-Negron. If it is useful to you, you can support its development, star it on GitHub, or report a bug.
Can I make a label as long as its content?#
Yes: tick Auto-length (continuous roll) in Label setup. See Labels with no fixed length.
How do I print 100 numbered labels?#
Put ${serial:4} in a text or barcode object, then use File → Print a number range…. See Numbered runs and sheets.
How do I put several labels on one A4 sheet?#
Use File → Print on a sheet…, choose A4 or Letter, and press Fit as many as possible. You can print it or save it as a PDF.
Can it make GS1 or pallet (SSCC) labels?#
Yes, with the GS1-128 and GS1 Data Matrix barcode types and the SSCC helper. See GS1 barcodes.
Where are my templates, logos, fonts, and addresses kept?#
In ThermalPrint's settings folder; see Where your data lives. Copy those folders to move them to another computer.
Can ThermalPrint check that a barcode scans?#
No. It checks that the value is valid for the type and that the bars are wide enough to print, but it does not read the barcode back. Scan the first physical label.
How do I change the language?#
ThermalPrint follows your system language (Spanish, German, or French; otherwise English). Change your system language and restart the app.