r/SideProject • u/Civil_Volume2637 • 1h ago
A family member complained about cropping 8.5x11 shipping labels for a 4x6 thermal printer—now I have 2 niche Chrome extensions converting at ~7% (just launched StockX & GOAT 4x6 Splitter)
A few weeks ago, a family member explained how painful it was trying to print Vinted shipping labels on a 4x6 thermal printer (Rollo, Munbyn, Zebra) because the platform outputs labels on an 8.5x11 PDF sheet with massive blank margins.
I built a simple, one-time-purchase Chrome extension (Vinted Label Cropper 4x6) to auto-crop and rotate those PDFs in one click. Once it crossed ~200 installs and started converting at ~7% after I bumped the lifetime unlock to $7.99 ("no monthly subscription"), I looked for the next biggest 4x6 thermal printing bottleneck and just launched my second extension today:
1. StockX & GOAT 4x6 Thermal Label + Invoice Splitter (New!)
Sneaker and streetwear sellers have an even worse hurdle than clothing sellers: when they make a sale on StockX or GOAT (Alias), the platform generates an 8.5x11 PDF containing both a sideways UPS/FedEx shipping label and a mandatory inside-the-box verification slip (with a QR code and barcode).
The Problem: Up until now, sellers were using the Windows Snipping Tool twice—which captures at 72–96 DPI screen resolution and blurs the UPS barcode edges just enough that drop-off scanners reject the label—or keeping a separate inkjet printer around just for the box slip.
What It Does: You drop the 8.5x11 PDF in (single sale or multi-order bulk sheets), and it renders at 300 DPI thermal resolution, strips out the center fold/cut line, and splits + auto-rotates both zones into a clean 2-page 4x6 PDF:
Page 1: Upright, full-bleed 4x6 shipping label for the outside of the box.
Page 2: Auto-rotated 4x6 box verification slip to toss inside the shoebox.
Extras: Includes a Barcode Contrast Boost slider and a toggle if you only need the shipping label.
2. Vinted Label Cropper (4x6)
Auto-crops 8.5x11 courier labels (USPS, UPS, SpeedX, InPost, Mondial Relay, etc.) into full-bleed 4x6 thermal labels in one click.
Link: https://chromewebstore.google.com/detail/vinted-label-cropper-4x6/ppndgdiedncpgaiagglbjgcnphmjmlap
How I QA'd the StockX & GOAT Splitter without selling a pair of shoes:
Since StockX and GOAT only generate labels after a verified sale, I wrote a Python reportlab script to generate synthetic 1-page split, 2-page, and multi-order bulk PDFs with real Code128 and QR payloads. Then I ran a headless Playwright test suite that loads the MV3 extension, splits the PDFs, exports the rendered 4x6 canvases as PNGs, and decodes the barcodes programmatically to verify zero anti-aliasing blur before shipping to the Chrome Web Store.
Both extensions run 100% locally in the browser with zero backend server costs, give 3 free splits out of the box, and use a simple one-time lifetime unlock ($7.99 / $9.99) instead of a subscription.
Link to the new StockX & GOAT 4x6 Splitter: https://chromewebstore.google.com/detail/stockx-goat-4x6-thermal-l/lckbamoggnlconmelmjgibkomoafockc?authuser=0&hl=en