Pick FLUX when raw photoreal quality, prompt control, and open weights matter most. Pick Seedream 4 when you need legible text inside the image, native 4K, multi-image edits, and the lowest cost per generation. That's the short version, and for most people one of those two sentences already points to the answer.
The longer version is more interesting, because these models were built by very different teams with different priorities. FLUX comes from Black Forest Labs, founded by the people behind Stable Diffusion, and it's aimed at being the photographer's model: faithful, flexible, and partly open. Seedream 4 comes from ByteDance's Seed team and is aimed at production volume: cheap, fast, 4K, and good at the things that usually trip image models up, like text. I've run both on real product and campaign work, so this is a hands-on read, not a spec-sheet recital.
Quick verdict: FLUX vs Seedream 4 at a glance
| FLUX (1.1 Pro / Ultra) | Seedream 4 | |
|---|---|---|
| Best for | Photoreal quality, prompt control, an open-weights option | Text-in-image, native 4K, matching sets, cost |
| Photorealism | Strongest overall, especially materials and skin | Very good, can skew glossy on people |
| Text rendering | Decent, still its weaker side | Class-leading, handles dense text |
| Max resolution | Up to 2K (1.1 Pro), up to 4 megapixels (1.1 Pro Ultra) | Native 4K, up to 4096px per side |
| Editing / multi-image | Available via FLUX.1 Kontext; less integrated | Built in, references up to ~10 images in one edit |
| Price per image | About $0.04 (1.1 Pro), about $0.06 (Ultra) on fal | $0.03 on fal |
| Open weights | Yes for FLUX.1 [schnell] (Apache 2.0) and [dev] (non-commercial); Pro/Ultra are API-only | No, API only |
| Where to reach for it | A specific look, art direction, on-device or self-hosted | High-volume catalog and social work that has to match |
Prices and specs are from Black Forest Labs, fal.ai's Seedream listing, and ByteDance's own materials, confirmed in May 2026. fal and other hosts change pricing, so check the live page before you budget a big run.
One thing to clear up first: "FLUX" is a family, not one model. The model this post anchors on is FLUX 1.1 Pro, the flagship API model, plus its Ultra variant for high resolution. Black Forest Labs has since shipped FLUX.2, which pushes photorealism further, but 1.1 Pro is the one most teams are running today and the one that maps cleanly against Seedream 4. Where FLUX.2 changes the math, I'll say so.
What each model actually is
FLUX 1.1 Pro is a 12-billion-parameter rectified-flow transformer. Black Forest Labs built it for speed and prompt adherence, and they claim up to 6x faster generation than the original Pro release. It generates up to 2K cleanly. The Ultra variant raises that to 4 megapixels at "ultra-fast" speeds, with a Raw mode that deliberately makes images look less synthetic, more like candid photography. That Raw toggle is a small thing that matters a lot if you're tired of the over-clean AI look.
The part that separates FLUX from almost everything else is licensing. FLUX.1 schnell ships under Apache 2.0, so you can run it locally and use it commercially for free. FLUX.1 dev is open-weight too, but non-commercial without a license. The Pro and Ultra models are proprietary, API-only. So "FLUX has open weights" is true and useful, but only for the schnell and dev tiers, not the flagship. If self-hosting or fine-tuning on your own GPUs is the deciding factor, that's a FLUX-only option here.
Seedream 4 is ByteDance's image model that folds generation and editing into one system. It outputs native 4K, up to 4096px per side, turns out 2K in seconds, and holds a subject consistent across a whole batch of images. The editing side is the standout: you can feed it multiple reference images, up to about ten, and give plain-language instructions like "put the product from image 1 into the scene in image 2." It's API-only, no open weights, and on fal it's $0.03 per image. We wrote a full Seedream 4 deep dive if you want the longer breakdown of its editing and consistency behavior.
Photorealism: FLUX wins, but it's closer than it used to be
If you handed me one prompt and said "make this look like a real photograph," I'd reach for FLUX first. It's better at the unglamorous stuff that sells realism: how metal catches light, how fabric folds, how skin reads as skin and not as rendered plastic. The Raw mode on Ultra leans into that even harder. For a hero product shot or an editorial-style image where the look is the whole point, FLUX has the edge.
Seedream 4 is genuinely good here, not a step down. Where it slips is people. The default lean is glossy and commercial, the kind of clean that looks great on a packshot and slightly fake on a portrait. You can prompt your way out with terms like "natural skin texture, available light, candid," and it'll comply, but the model wants to make things pretty. For product on a surface, that bias is fine. For a documentary or gritty look, FLUX gets there with less fighting.
Worth flagging: FLUX.2 narrows or closes this gap depending on whose head-to-head you read. The reputable roundups in 2026 land on FLUX for photorealism and Seedream for text-heavy production, which matches what I see.
Text rendering: Seedream 4 wins, clearly
This is the cleanest call in the whole comparison. Legible text inside an image has been the embarrassing failure of image models for years, and Seedream 4 mostly solved it. It renders dense text, multi-line layouts, even formulas and tables in ByteDance's demos. FLUX is decent and has improved, but it still trails. If your output has a headline, a label, a price, or any real words baked into the pixels, Seedream saves you a round-trip to Photoshop that FLUX often won't.
For a social team pushing campaign graphics with copy on them, this one feature can decide the whole thing.
Editing and multi-image: Seedream 4 is more integrated
FLUX does editing through FLUX.1 Kontext, which is strong, and Kontext dev is open-weight. But it lives a little to the side of the main generation model. Seedream 4 was trained with generation and editing together, so the edit behavior feels like part of the same brain. Swap a background, relight a scene, drop a product from one image into another, and it tends to leave the rest of the frame alone. ByteDance reports Seedream came out ahead on MagicArena's single-image editing ratings, edging past Gemini 2.5 Flash Image; that's their benchmark, so weight it accordingly, but it lines up with hands-on use.
The multi-image part is where Seedream pulls clearly ahead for production. Referencing up to ten images in a single edit, with natural-language instructions, is exactly what catalog and campaign work needs. FLUX can be wrangled into consistency with seeds and references, but it's more work.
Price: Seedream 4 is cheaper, and it adds up
On fal, Seedream 4 is $0.03 per image. FLUX 1.1 Pro is around $0.04 and Ultra around $0.06. On a single image, nobody cares. On a campaign where you burn through 300 attempts to land 20 keepers, that's $9 versus $12 to $18, and the gap widens the more you iterate. For high-volume, throwaway-heavy work, Seedream is the value pick by a clear margin. For a handful of hero images where quality is everything, the price difference is noise and you should just pick the better output.
Which should you use?
For product photography and ecommerce catalogs
Lean Seedream 4. The subject-consistency feature keeps the same bottle or sneaker identical across ten contexts, the editing handles background swaps without redrawing the product, and the price lets you iterate freely. Reach for FLUX on the one or two hero shots where you want a specific, art-directed look that Seedream's clean default won't give you.
For social graphics with text on them
Seedream 4, almost every time. The text rendering is the reason. You'll spend less time in an editor fixing garbled words.
For editorial, portraits, and a specific aesthetic
FLUX. Better skin, better materials, the Raw mode for a candid feel, and stronger response to precise art direction. Seedream can get there but fights you toward glossy.
For self-hosting, fine-tuning, or on-device
FLUX is the only option here. FLUX.1 schnell under Apache 2.0 runs commercially for free on your own hardware; dev is open-weight for non-commercial use. Seedream has no open weights at all.
For high-volume throwaway iteration
Seedream 4, on cost alone. Three cents an image changes how freely you experiment.
Where each one falls short
FLUX's honest weaknesses: the flagship Pro and Ultra are proprietary, so the open-weights story only applies to schnell and dev. Text rendering still trails Seedream. And per image it costs more, which stings on big runs. It can also lean a touch stylized unless you steer it toward realism.
Seedream 4's honest weaknesses: it skews glossy on people, so it's not the first pick for gritty or documentary looks. Fine compositional control is loose; if you have an exact layout in your head, you'll fight it more than a model with explicit region controls. Full 4K renders take longer than the "few seconds" headline, which is for 2K. And like every model in this class, it'll confidently get a small detail wrong, a logo, a hand, an object count, in a way that looks right until you check. Somebody still has to look closely before it ships.
Don't pick one. Run both.
The smart move isn't betting a whole workflow on a single model. It's keeping both on hand and sending each job to whichever wins it. On Masonry you can run Seedream 4 and FLUX on the same canvas, fire the identical prompt at both on your own input image, and keep the better result. For product and campaign work especially, that side-by-side is the fastest way to learn which model handles your particular files before you commit a deadline to it. Browse the full lineup on the models page.
FAQ
Is FLUX or Seedream 4 better for photorealism? FLUX, in most head-to-heads, especially for materials and skin. Seedream 4 is close and very good, but its default look skews glossy on people. FLUX.2 widens FLUX's lead further. For a specific photographic look, FLUX; for clean commercial product shots, either works.
Which one is better at rendering text inside the image? Seedream 4, clearly. It handles dense text, multi-line layouts, and small type far better than FLUX. If your image has words baked in, this is the deciding feature.
Can FLUX do 4K like Seedream 4? Sort of. FLUX 1.1 Pro tops out around 2K, and the Ultra variant reaches 4 megapixels. Seedream 4 generates native 4K up to 4096px per side. For true 4K production assets, Seedream is the simpler answer.
Which is cheaper? Seedream 4 at $0.03 per image on fal, versus roughly $0.04 for FLUX 1.1 Pro and $0.06 for Ultra. On high-volume runs the difference adds up; on a few hero images it's noise.
Does FLUX have open weights and Seedream 4 doesn't? Yes. FLUX.1 schnell is Apache 2.0 (free commercial use), and FLUX.1 dev is open-weight for non-commercial use. The flagship Pro and Ultra are API-only. Seedream 4 has no open weights and is API-only.
Can I use both FLUX and Seedream 4 together? Yes. On Masonry you can run both on one canvas with the same prompt and input, then keep whichever output wins. See the model lineup and the Seedream 4 deep dive for more.
