Rename Photos for Amazon Bulk Upload (SKU.MAIN, PT01)

Published 28 September 2026 · by Tekiba

For a bulk upload, Amazon works out which listing and which slot a picture belongs to from its file name: the product's identifier, a full stop, a four-character variant code, and the extension — B00431765.MAIN.jpg for the main image, B00431765.PT01.jpg onwards for the rest. SignetDrop renames and resizes a batch that way in your browser and hands back one ZIP. The numbering is free, ten photos at a time, up to 2048px; a fixed name for any file is paid.

What the style guide says about file names

The source here is Amazon's Amazon Home Selection Style Guide, a PDF read on 28 September 2026. It is written for the Home category and is dated 2017 in its file, so treat it as one category's rules rather than Amazon's for every product. Its naming page starts from the whole:

The file name is comprised of the product identifier, the variant code, and the image type suffix.

Then it gives one example, "Example: B00431765.PT02.jpg", and takes the three parts in turn. The identifier is "Either the Amazon ASIN code or UPC/EAN with no dashes, spaces or other punctuation." The variant code is four characters: MAIN for the primary image, which the guide describes as "the first image the customer will see when they click into the detail page", then part shots numbered from PT01, and environmental images numbered from EV01. The extension is the file type; JPEG is the one it prefers.

Its examples page shows one MAIN, then PT01, PT02 and so on, with an ASIN and a numeric UPC.

Why the variant code matters

The upload page of Amazon's guide has the sentence that makes naming worth the care:

If the file name does not include a 4-character variant, the image will be treated as MAIN

It goes on to say that this "could then accidentally overwrite an existing main image". So a file called B00431765.jpg is not a harmless shorthand for a main photo; it is a main photo whether you meant it or not. Numbering every additional picture, and keeping MAIN for the one you chose, is how a batch lands in the slots you intended.

The same page describes the bulk route in three steps — name the files, "Create a zip file and copy image files to zip.", then upload the ZIP. It is written for Vendor Central. Seller Central has its own help pages on image uploads, which need a login; check them for your account as well, since the two may not agree and we have not been able to read them.

Size and the rest of the file rules

Names are one of four file rules on Amazon's requirements page. The other three:

Color profile must be sRGB.

Image size must be a minimum of 2000 pixels

Images cannot include text, graphics, or logos.

The size rule is per side, and it is where the free version falls short for most photos. Free output stops at 2048px on the longest edge and never enlarges, so a 4000×3000 photo becomes 2048×1536 — the long side clears the minimum and the short side does not. A square photo at 2048px clears it on both sides. For anything else, the paid version lifts the ceiling: set the long edge to 2667 and a 4:3 photo's short side lands on 2000. Other categories set other figures, so read the guide for yours before choosing one.

The last rule rules out a watermark on these pictures, so leave it off for an Amazon batch.

Doing it to a batch here

The free route numbers the part shots; the main image is named separately. Drop in only the additional photos for one product, in the order you want them numbered.

Set the names. Choose Numbered, put the identifier, a full stop and PT in the prefix — B00431765.PT — start at 1, and set Digits to 2. Five photos come out as B00431765.PT01.jpg to B00431765.PT05.jpg. With Digits left at 0 the width follows the batch, and under ten photos that gives PT1 rather than PT01.

Numbered, with the identifier and PT in the prefix and two digits.
Set the size and format. Choose the longest edge and JPEG. Nothing is ever enlarged.
Run the batch and take the ZIP. The archive is built in the page; nothing is uploaded to build it. The files inside carry the names from step 1.

A free run of five part shots, ready to download as one ZIP.

For the main image, the paid Template mode takes fixed text, so B00431765.MAIN names a single photo exactly. On the free version, name that one file yourself, or use Original name plus a suffix with .MAIN on a photo already named after its identifier.

What this does not do

It does not look anything up: a wrong ASIN is renamed as readily as a right one. It does not talk to Amazon, so the ZIP reaches your account only when you send it. And it settles nothing on Amazon's side — which name Amazon accepts for your category is Amazon's call, not ours, and this page is only what one of its guides said on 28 September 2026.

Where the free version stops

Free does ten photos at a time, up to 2048px on the longest edge: resize, convert, rename, watermark and a ZIP, with numbering to any width. Sizes past that, templates with fixed text and saved presets are paid, $29 once — the split is on the pricing panel.

Open SignetDrop and try a batch. The free settings need no account, and the pictures stay on your disk.

Questions

What happens if an Amazon image file has no variant code?

The guide is plain about it: "If the file name does not include a 4-character variant, the image will be treated as MAIN". It warns that this can overwrite the main image you already have, which is the reason to name every file before it goes into the ZIP.

Can I put a watermark on Amazon product photos?

Not under this guide: "Images cannot include text, graphics, or logos." Leave the watermark off for this batch. If you want a marked set for your own site as well, run the same photos a second time with a mark on and a different name.

Can I do this for free?

The numbering, yes: Numbered with a prefix and Digits set to 2 is free, ten at a time on the free version, up to 2048px, with nothing uploaded. A fixed name such as B00431765.MAIN for any file, and sizes past the free ceiling, are the paid side, $29 once.

Open the tool, or read about bulk resizing and renaming, what eBay and Etsy allow on a listing photo, watermarks on real estate listings, clearing location data, whether resizing removes EXIF, fitting square photos to a 3:4 frame, sizing for a feed, watermarking a batch or squaring a batch without cropping, or what this page loads and counts.