Allegro Image Requirements: Two Rulebooks, One Listing

Allegro image requirements are two rulebooks wearing one name. The first photo you upload — the thumbnail — must not carry a single unit of measurement. Every photo after it may carry product dimensions in figures and units, plus arrows, cross-sections and close-ups. Same listing, same product, opposite rules.

Most sellers find this out the expensive way: they build one annotated hero image, set it as the first photo, and lose it. The mark that earns a gallery photo its keep is the same mark that gets a thumbnail pulled.

Allegro image requirements start with one question: which photo is this?

Before you check pixels or backgrounds, answer one question about the file in front of you. Every one of the Allegro image requirements hangs off it.

• Is it the first image in the listing form? → It is the thumbnail. Strictest rules. No text, no logos, no units of measurement. Go to Branch 1.
• Is it any other photo in the gallery or in the description? → Gallery rules. Backgrounds are free, dimensions in figures and units are allowed, descriptive sentences are not. Go to Branch 2.
• Was it generated or materially modified by AI in a way that could pass as real? → Whichever branch it sits in, the EU transparency layer applies on top. Go to Branch 3.
• Is it a brand infographic pulled from BrandHub? → It is neither: you cannot make one yourself, and it can never be the thumbnail.

A thumbnail, in Allegro's own definition, is simply the image you set first in the listing form — it is what buyers see on the product list. Nothing about the file makes it a thumbnail; position does.

Branch 1: the thumbnail

Background: one rule, then a list of exceptions

Allegro's help page is blunt about the default: "There is only one rule — use only white background (RGB 255.255.255)." Borders and other adornments are out. White or transparent products still present acceptably against white.

Two sets of exceptions matter for exporters:

Uniform white or uniform light gray (in the HSV model, a V value not lower than 0.8) is accepted in Fashion — Clothing, Footwear and Accessories; Kids — Clothing; Kids — Footwear; and Sports and Travel — Travel — Luggage, Clothing and Footwear. This applies to business and regular accounts alike.

Non-white backgrounds are permitted in a long, category-by-category list that the help page enumerates individually. It includes used, remanufactured or damaged items; automotive parts sold in that condition from a business account; fashion sold at auction; furniture sets, beds and couches; flooring, parquet, laminate, floor tiles and wallpaper; plants; live animals; real estate; services; and products delivered by email. If you sell furniture or building materials into Poland, check your exact category against that list before you spend money reshooting on white — you may be allowed a room set, which is a different and usually better photo. The same product then needs a separate furniture spec diagram further down the gallery, where the measurements are legal.

What you may not add — this is where dimensions die

The thumbnail exists to show the product and nothing else. Allegro's rules, quoted:

• "Do not add any text in the background."
• "Do not add any icons or graphics (for example, arrows pointing to a specific part of the product)."
• "Do not place any logotypes — of a product or of your store." The exception is designer products where a logo appears on the item or its packaging.
• "A thumbnail must not contain additional graphic elements, such as logotypes, units of measurement, etc."

That last line is the one to print out. A dimension callout on an Allegro thumbnail is a rule breach, not a style choice. There is one narrow escape hatch: if a crucial feature such as colour, flavour or scent cannot be depicted photographically, you may add graphic elements to the thumbnail to indicate it. Size is not on that list, because size can be photographed — badly, but it can.

What the thumbnail may include

• Models, with the product, in any category. Note that images with recognisable faces get hidden from the Allegro Product Catalog and the product change request form by an automated check.
• A second shot of the same product from another angle in the same frame, as long as buyers cannot mistake how many units they are buying.
• A demonstrative item that clarifies the purchase — Allegro's example is a car radio shown with its remote.
• The original manufacturer's packaging, provided your store logo is not on it.

Size limits

Maximum upload resolution is 26 Mpx. The largest size Allegro displays is 2560 × 2560 px, and anything with a side longer than 2560 px is scaled proportionally to fit. The longer side of a thumbnail must be at least 400 px.

Branch 2: gallery and description images

This is the branch that pays for a spec-diagram workflow, because the allowances are unusually generous.

What is allowed, and what is not

Exceptions can exist where you have an agreement with an authorised distributor.

The line between "graphic" and "description"

Two consecutive lines in Allegro's help page do all the work:

"You can describe the product dimensions with figures and units of measurement."
"Do not add any descriptions of the height or length. Present such information graphically."

Read that as a format rule, not a content ban. Allegro is not telling you to hide the dimensions — it is telling you to draw them instead of writing them. An arrow spanning the seat width with "48 cm" beside it is compliant. A caption reading "Height: 82 cm, Width: 48 cm — perfect for small apartments" is not, on two counts: it is a written description of the height, and the second half is a product-feature claim in text.

The same instinct trips people up on other marketplaces in the opposite direction, which is why the safe habit is to keep written copy in the listing fields and keep numbers on the image — see text size on product images for the legibility side of that trade-off.

Technical limits and how many photos you get

Note the mismatch worth remembering: the thumbnail floor is 400 px on the longer side, the gallery floor is 500 px. Build to 2560 px and neither applies.

Infographics are a fourth category

An Allegro infographic is not a photo you can produce. Access runs through the BrandHub tab in Sales Center, which is invite-only, and the materials come from official brands and manufacturers. You cannot create them yourself, and an infographic cannot be used as a thumbnail. If you cannot find one for your product, there isn't one. Your annotated gallery images are the substitute.

Branch 3: was the photo touched by AI?

This layer is new and sits on top of both branches. Allegro's seller help ties it to Regulation (EU) 2024/1689 — the EU AI Act — and states that the transparency rules take effect on 2 August, with the labelling option available in the Allegro Product Catalog, the listing form, file uploads and the API by that date at the latest. Applying it adds an AI watermark to the photo.

The scope is narrower than "any AI touched this file". Allegro describes it as applying to images generated or modified by AI that might appear authentic — deepfake-type content. Its own examples:

• photos generated from scratch, for instance when a made-to-order product does not exist yet
• photos of a real product with an AI-generated background
• virtual models, meaning AI-generated characters presenting the product

Three consequences for a supplier:

1. You own the declaration. Allegro states plainly that assessing the photo and deciding whether to label it is the seller's responsibility, and that it does not automatically verify every photo.
2. Your supplier's images are your problem. Allegro recommends asking suppliers whether the materials they provide were generated or modified using AI. If you resell a factory's catalogue images, that question belongs in your onboarding checklist.
3. The clock is running on detection. Allegro notes that from 2 December 2026, AI tool providers will be required to add metadata about AI use to files, and that it is considering using that metadata in future.

Once a photo is saved, its AI declaration can no longer be changed. Decide before upload, not after.

The decision matrix

Allegro image requirements, reduced to one table you can keep beside the retouching queue.

Building the set without breaking either rulebook

A production order that survives both branches:

1. Shoot the product clean on white first. That file is the thumbnail, and it stays untouched — no arrows, no callouts, no "48 cm".
2. Duplicate it and build the dimension image second, from the same frame. Same product, same angle, numbers added. It goes in slot 2 or 3.
3. Keep every written claim — materials, capacity, compatibility, room recommendations — in the offer description and parameters, where text belongs.
4. Check your category against the background exception list before reshooting anything on white.
5. Decide the AI declaration before upload, for every image, including supplier-provided ones.

The pattern repeats across European marketplaces with different thresholds each time, which is why it pays to diff them rather than assume — Kaufland product image requirements and Bol.com product image requirements draw the text line in noticeably different places.

Pre-upload checklist

• The first image in the listing form carries no text, logo, arrow or unit of measurement
• Thumbnail background is white (RGB 255.255.255), or a listed exception applies to your exact category
• Thumbnail longer side is at least 400 px; gallery images at least 500 px
• Dimensions appear only on gallery images, drawn graphically, never written as sentences
• No store name or logo appears on any image, including on packaging shots
• Feature claims, structure explanations and spec tables live in the description, not on the image
• File formats are JPG, JPEG or PNG (WEBP only via API or file upload), in sRGB
• Image count is within 10 (regular) or 16 (business, non-classifieds)
• Every AI-generated or AI-modified image has its declaration decided before saving
• Supplier-provided images have been checked for AI generation

FAQ

Can I put dimensions on my Allegro product photos?

Yes — on gallery images, not on the thumbnail. Allegro's rules say "You can describe the product dimensions with figures and units of measurement" for gallery and description images, while the thumbnail "must not contain additional graphic elements, such as logotypes, units of measurement, etc." The same page adds the format instruction: present dimension information graphically rather than as written descriptions of height or length.

That is a production requirement more than a design one. It means the number on the image has to be the measured number, drawn as a dimension line that actually spans the part it labels — because a marketplace rule that pushes size information out of text and onto the picture also removes your chance to hedge it in a sentence. Software that snaps a measurement to the real edges of the product in the photo, keeps the scale consistent across a whole SKU set, and exports at each marketplace's pixel spec does this in minutes per listing. An AI image generator does not: it can render a plausible-looking "48 cm" onto a chair it never measured, which is exactly the kind of number that turns into a return.

What size should Allegro photos be?

Build to 2560 × 2560 px and the Allegro image requirements for size stop being a constraint. 2560 px is the largest size Allegro displays, and anything with a longer side above it gets scaled proportionally. The floors are lower — 400 px on the longer side for a thumbnail, 500 px for gallery and description images — and the upload ceiling is 26 Mpx. Any aspect ratio is accepted for gallery images.

Does Allegro require a white background?

For the thumbnail, yes by default: white, RGB 255.255.255. Fashion, kids' clothing and footwear, and travel luggage/clothing/footwear categories also accept a uniform light gray with an HSV V value of at least 0.8. A separate list of categories — used and damaged goods, fashion auctions, furniture sets, beds, couches, flooring, wallpaper, plants, live animals, real estate, services and more — permits other backgrounds entirely. Gallery images have no background restriction at all.

How many photos can I add to an Allegro offer?

Ten on a regular account, sixteen on a business account outside classifieds, and forty on a business account in a classified listing.

Do I have to label AI-generated photos on Allegro?

If the image is generated or modified by AI in a way that could pass for authentic, the EU AI Act transparency obligation applies and Allegro provides a labelling option that stamps an AI watermark on the photo. Allegro's examples are fully generated product shots, real products dropped onto AI-generated backgrounds, and AI-generated virtual models. Allegro states that the judgement is the seller's, that it does not check every photo automatically, and that the declaration cannot be changed once the photo is saved. It also recommends asking your suppliers whether their images were AI-generated — for a reseller, that question is the whole compliance exercise.

Sources & References

• Allegro Help for sellers — What a thumbnail is and how to set it according to our rules (white background RGB 255.255.255, 400 px minimum, 26 Mpx, no units of measurement, category exception lists)
• Allegro Help for sellers — Rules for images in the gallery and in descriptions (500 px minimum, 2560 × 2560 px, formats, image counts, allowed graphic elements, dimensions with figures and units, BrandHub infographics)
• Allegro Help for sellers — Labeling AI-generated or modified photos, frequently asked questions
• Allegro Help for sellers — Rules for images (category index, including when a photo can be removed from an offer)
• EUR-Lex — Regulation (EU) 2024/1689 laying down harmonised rules on artificial intelligence (AI Act)