troubleshooting · esc-pos
Barcode Not Printing
Quick answer
Validate the data against the chosen symbology before printing. Then confirm printer support, command syntax, length/terminator rules, width, height, quiet zones, and media quality. A visible barcode is not successful until the exact encoded value scans reliably.
Diagnose it
- Identify the symbology and validate allowed characters and check digits.
- Test the printer manufacturer’s minimal example.
- Verify the command form expected by the specific model.
- Check data length, terminator, and Code 128 subset switching where applicable.
- Disable human-readable text temporarily to isolate the bars.
- Increase height and ensure the full width fits the printable area.
If it prints but will not scan
- Restore left and right quiet zones.
- Avoid horizontal scaling or excessive narrow-bar width.
- Improve thermal darkness and reduce speed if appropriate.
- Print perpendicular to defects where label design permits.
- Clean the printhead and test fresh media.
- Scan with more than one configured scanner.
Never use a screenshot of a barcode without controlling its pixel dimensions. Prefer the printer’s native generator or a purpose-built renderer with known module width.
Verify
Compare the decoded scan to the source byte-for-byte, then test short, long, numeric, and edge-case values on production media.
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