Seedream 5.5 vs 5.0 Pro: what actually changed

Seedream 5.5 vs 5.0 Pro: the four changes that matter

The layer ceiling goes from 16 to 99. Both models can decompose a single finished image into a base image plus independently editable PNG layers, which is the feature that makes a generated poster behave like a design file. 5.0 Pro returns one base image and up to 16 layers; 5.5 returns one base image and up to 99. A dense promotional layout with a dozen text elements, several product shots, badges and background furniture is the case that used to hit the ceiling and get merged into fewer, coarser layers.

You also get to set that ceiling. 5.5 adds a cap on the total number of images a decomposition returns, anywhere from 2 to 100 including the base image, defaulting to 30. When a prompt does not say how to split the image, the model plans the breakdown against that cap, so a higher number generally buys a finer decomposition. 5.0 Pro has no equivalent control.

Text layers come back as text. This is the genuinely new capability. Ask 5.5 to recognise formatted text during a decomposition and each standard text layer returns structured recognition alongside its PNG: the full string, a bounding box per line, and the line split into runs that each carry a closest-matching font name, a hex colour, and flags for bold, italic, underline, strikethrough, shadow and translucency. The documented font matching covers 101 common Chinese fonts and 127 common fonts in other languages. 5.0 Pro has no text recognition at all, so reading a headline off a generated layout meant doing it by eye.

Transparent output moved upstream. In 5.0 Pro a transparent background is an image-to-image operation only: one input image, which has to be a PNG that already has an alpha channel. In 5.5 both text to image and image to image can return a transparent or semi-transparent background, inputs can be up to ten images with no alpha requirement, and the default is a new automatic mode where the model decides from the prompt and the output format. Native RGBA straight out of a first generation is the difference between a cutout pass and no cutout pass.

Specs side by side

The resolution tiers are identical, which is worth saying plainly: if 2K was enough before, nothing about the output size forces a move. The 8.29 megapixel ceiling documented for 5.5 is the number behind the 4K claim, since 3840 by 2160 lands exactly on it.

What stays the same

Both models generate from text, take up to ten reference images for image-to-image work, and support interactive editing where you point at a region and describe the change. Both decompose an image into a base plus alpha-channel PNG layers, and both return the position, stacking order, name and description of every layer they produce. Neither does image group generation, and neither searches the web.

The sizing story is mostly unchanged too. Single-image generation offers the same three resolution tiers with the same 2K default, and layer decomposition offers the same tiers plus an automatic mode that keeps each layer close to its original dimensions.

What 5.5 gives up, and what to plan around

Two things get narrower. The fast prompt-optimisation mode is gone: 5.5 accepts only the standard mode, which is described as higher quality and slower, and passing the fast option returns an error. And the default output format flips from jpeg to png, so a pipeline that relied on the default to keep files small needs to ask for jpeg explicitly. Asking for jpeg and a transparent background together is a contradiction and errors out.

Three habits are worth building if you lean on decomposition. It is all or nothing: if any single layer fails, the whole request errors rather than returning a partial result. If the split a prompt asks for exceeds the cap you set, some layer detail is lost rather than queued, so the cap is a real decision and not a safety net. And quota is reserved against the cap you set rather than what the model actually returns, with the unused portion released afterwards, so an inflated cap briefly holds capacity you never use.

The text recognition has honest edges as well. It only fires on text the model judges to be standard, so artistic lettering and handwriting return a layer with no recognition attached. The font name is the closest visual match rather than the font in the original file, and it comes back as unknown when confidence is low. Treat the styling it reports as a very good starting point for a rebuild, not as a spec sheet.

Which one should you use

For anything where a generated image is the start of a layout rather than the end of one, 5.5 is the clear answer whenever it lands: 99 layers instead of 16, text that comes back readable with its styling, and transparency available in a first-pass generation. Those three together change the workflow, because the handoff from generation to assembly stops being a manual rebuild.

For everything else the gap is smaller than the feature list suggests. If you generate single finished images at 2K and never take them apart, the resolution tiers, the reference-image budget and the editing model are the same, and 5.0 Pro also keeps the fast prompt-optimisation mode that 5.5 drops.

The practical constraint is availability. Seedream 5.0 Pro runs on Morphic now; 5.5 is announced with its public API document still to be published, and no pricing has been shared, so cost per image is an open question rather than a comparison point. Prompts transfer either way, since the two take the same instructions and the same editing habits.

Using Seedream on Morphic today

Seedream 5.0 Pro sits in the Morphic image model line, next to the rest of the catalogue, and it is the model the examples in our Seedream 5.5 prompt library were rendered on. Write the image as a brief, generate, and the result lands on the Canvas, where the same brief can run through another model for a side-by-side read.

Morphic also covers part of the layered workflow itself, independent of which Seedream version you are on. Smart Select and Point Select segment a generated image on the Canvas, with options to separate an element as a layer, exclude the background or erase an object, and segments export as PNG, JPEG or WebP. That is how you lift a product off its background today without waiting for a decomposition call.

For the prompt mechanics, read the Seedream 5.5 guide. For the full specification of either model, see the Seedream 5.5 model page or the Seedream 5.0 Pro model page, and for editing, the Seedream 5.5 AI image editor.