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    GGUF: FastFlux (Flux.1-Schnell Merged with Flux.1-Dev) - Q5_0_v2
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    [Note: Unzip the download to get the GGUF. Civit doesn't support it natively, hence this workaround]

    Flux1.D merged in Flux1.S. It can generate good-quality images (better than Schnell) with just 4 steps, and the quality further improves with more steps, while consuming a very low amount of VRAM. Q_4_0 can produce 1024x1024 images in 45 seconds on my 11GB 1080ti, while using around 6.5 Gigs of VRAM.

    It can be used in ComfyUI with this custom node or with Forge UI. See https://github.com/lllyasviel/stable-diffusion-webui-forge/discussions/1050 to learn more about Forge UI GGUF support and also where to download the VAE, clip_l and t5xxl models.

    Which model should I download?

    [Current situation: Using the updated Forge UI and Comfy UI (GGUF node) I can run Q8_0 on my 11GB 1080ti.]

    Download the one that fits in your VRAM. The additional inference cost is quite small if the model fits in the GPU. Size order is Q4_0 < Q4_1 < Q5_0 < Q5_1 < Q8_0.

    • Q4_0 and Q4_1 should fit in 8 GB VRAM

    • Q5_0 and Q5_1 should fit in 11 GB VRAM

    • Q8_0 if you have more!

    Note: With CPU offloading, you will be able to run a model even if doesn't fit in your VRAM.

    LoRA usage tips

    The model seems to work pretty well with LoRAs (tested in Comfy). But you might need to increase the number of steps a little (8-10).

    Updates

    V2: I created the original (v1) from an fp8 checkpoint. Due to double quantization, it accumulated more errors. So I found that v1 couldn't produce sharp images. For v2 I manually merged the bf16 Dev and Schnell checkpoints and then made the GGUF. This version can produce more details and much crisper results.

    All the license terms associated with Flux.1 Dev and Flux.1 Schnell apply.

    PS: Credit goes to jice and comfy.org for the merge recipe. I used a slightly modified version of https://github.com/city96/ComfyUI-GGUF/blob/main/tools/convert.py to create this.

    Description

    Bigger than Q4, should be better than Q4

    FAQ

    Comments (66)

    zombiehellmonkeyAug 20, 2024· 3 reactions
    CivitAI

    V2 is faster on my computer than V1. Thank you so much for making this!

    BilboTagginsAug 21, 2024· 2 reactions

    this has been my experience as well, for some reason there is less down time between loading the model and the clips/vae.

    amazingbeautyAug 21, 2024

    it give me black image

    xhorxhiAug 20, 2024· 1 reaction
    CivitAI

    this works very well for me however if i add lora it doesn't seem to do anything

    pretty_pixels
    Author
    Aug 20, 2024

    You might need to increase the number of steps a bit

    JayNLAug 21, 2024· 1 reaction

    Did the LoRA's work with other GGUF models? If not update Unet Loader

    xhorxhiAug 21, 2024· 1 reaction

    @nakif0968 increasing the strength of the lora to > 2 seem to work, but not all loras have the desired effect, but the ones that do work incredibly well.

    pretty_pixels
    Author
    Aug 21, 2024

    @xhorxhi Yes, try updating the Comfy + GGUF node too like @JayNL mentioned

    fablegeniusAug 21, 2024· 2 reactions
    CivitAI

    civitai shows the Q8 model being 11.82 GB but downloaded it's 12.7 GB. wonder why, and I wonder if I can use it with my 12GB 3060. edit: it works. detail isn't great at 4 steps, need to look into this more.

    pretty_pixels
    Author
    Aug 21, 2024· 1 reaction

    If you're not satisfied with the detail, try cranking the steps a bit. It should improve up to 12 steps.

    pretty_pixels
    Author
    Aug 21, 2024· 1 reaction

    Another tip, if you refine(Comfy)/img2img(Forge) using the Dev model with a denoise of ~0.4 and 20x0.4=8 steps you can gain back a lot of detail and expressivity. Use this model for quick iteration, and use Dev model to finalize the good ones.

    amazingbeautyAug 21, 2024
    CivitAI

    black image all time with q_41_v2 any solution ?

    pretty_pixels
    Author
    Aug 21, 2024· 1 reaction

    Which UI are you using?

    amazingbeautyAug 21, 2024

    @nakif0968 comfyui i'm using the cpu , which detail i can provide to more to let know why this problem ?

    pretty_pixels
    Author
    Aug 21, 2024· 1 reaction

    @amazingbeauty Seems like a Comfy problem. Raise an issue at the Comfy UI Github repo for CPU inference with GGUF.

    amazingbeautyAug 22, 2024· 1 reaction

    @nakif0968 who will listen to cpu user between most of people with thousands of dollars or hunderds gpu..!!

    i will forget about it

    ishadowxxAug 22, 2024· 1 reaction

    @amazingbeauty use a different scheduler. If you had been using Euler + Simple and got the black image, try the SGM-Uniform. If nothing changed then use the Sampler DPM++2M + Simple. If neither work, use a different text encoder/VAE combo.

    EtZetaAug 23, 2024

    @ishadowxx Where i can find a better text encoder/vae?

    mirek190Aug 21, 2024· 2 reactions
    CivitAI

    Make gguf Q4k_m instead of "old" Q4, Q4.1 or Q5 please.

    Q4k_m has quality of "old" Q5.1

    MysticDaedraAug 22, 2024· 1 reaction
    CivitAI

    Which quant should I (we...) select for this kind of quantization in SD Forge? I'm only familiar with the regular Stable Diffusion quants (FP/BF/NF), I don't really understand how those translate to LLM quants. SD Forge also doesn't have a selection of Q quants either... so which should we select, FP16? FP8?

    pretty_pixels
    Author
    Aug 22, 2024· 1 reaction

    Just use "Automatic" setting. It will detect it by itself. And regarding which you should download, I'd recommend trying from the biggest model Q8_0, given you have >8Gigs of VRAM.

    MysticDaedraAug 22, 2024· 1 reaction

    @nakif0968 I'll give it a try for sure! Currently doing a LoRA grid right now, so running 4_1, about 27 seconds per inference, for noticeably higher-quality images than finetuned SDXL... and Flux is still a baby! I can't even imagine what this model will be capable of after a few generations of finetunes and merges...

    Anyways, thanks for sharing, keep up the good work!

    MysticDaedraAug 22, 2024· 1 reaction
    CivitAI

    SD Forge says "Distilled CFG Scale will be ignored for Schnell". Does this mean I should adjust the regular CFG as needed?

    pretty_pixels
    Author
    Aug 22, 2024· 2 reactions

    No, unfortunately since this is a Schnell model, you don't have CFG/guidance control. So, basically, you're stuck with the prompt sensitivity baked into the model, you cannot turn it up/down.

    MysticDaedraAug 22, 2024

    @nakif0968 So nothing I can do to reduce the general over-baked quality compared to dev? So far every image I've made with Schnell has resulted in what I would normally consider to be too high CFG in SDXL etc.

    pretty_pixels
    Author
    Aug 22, 2024· 2 reactions

    @MysticDaedra Unfortunately, no. It has to be done via LoRA or prompt tricks. You may also try different samplers, but no CFG for now.

    pretty_pixels
    Author
    Aug 31, 2024

    @MysticDaedra You might want to try HyperFlux, which has CFG control https://civitai.com/models/705444/gguf-hyperflux-8-steps-flux1-dev-bytedance-hypersd-lora

    shiccupAug 23, 2024
    CivitAI

    I don't think combining shnel with dev fixes the licensing its still noncommercial

    pretty_pixels
    Author
    Aug 25, 2024

    Yes

    unphasedAug 24, 2024
    CivitAI

    asking for Q6_K. It is the highest one that runs without swapping on my 12GB setup in linux.

    pretty_pixels
    Author
    Aug 24, 2024

    You mean swapping the text encoder? because Q8 should fit in 12 Gigs.

    pretty_pixels
    Author
    Aug 24, 2024

    BTW... I don't know how to make K/S quants yet, because gguf-py doesn't support that yet.

    JayNLAug 29, 2024

    Q8 works fine on 4070 12GB, doesn't even slow down Windows, only F16 makes my PC useless to do anything else.

    MysteriomAug 24, 2024· 8 reactions
    CivitAI

    I'm with 3060 12G, Q4_1, 4steps, 1152*896.
    Just 32 seconds for 1 photo, that's impressive for me

    SuzanneAug 25, 2024
    CivitAI

    AssertionError: You do not have T5 state dict!

    what does it mean ?

    pretty_pixels
    Author
    Aug 25, 2024

    If you're using forge see: https://github.com/lllyasviel/stable-diffusion-webui-forge/discussions/1050 regarding where to put these models and how to use them.

    SuzanneAug 31, 2024

    @nakif0968 thanks for your reply, but now I have this new error message but only with this model,

    AssertionError: You do not have VAE state dict!

    https://civitai.com/models/618692/flux?modelVersionId=691639

    tristan22mcAug 25, 2024
    CivitAI

    Im confused about there being a Q4_0 and Q4_1 whats the difference?

    pretty_pixels
    Author
    Aug 25, 2024

    Size vs quality. Bigger size -> better quality, but also more VRAM required

    tarzthegray700Aug 26, 2024· 2 reactions
    CivitAI

    I'm not familiar with GGUF. Does it only integrates as a node in ComfyUI workflow? Or would it be possible to use it as a model in A1111?

    pretty_pixels
    Author
    Aug 26, 2024

    You can use it forge ui

    tarzthegray700Aug 26, 2024

    @nakif0968 oh cool. Thanks, I'll take a look.

    rostamianiAug 30, 2024· 3 reactions
    CivitAI

    What's the benefit of merging these two?

    Can you compare this with Flux.1 dev gguf 8 in vram/speed/quality?

    SyamsQOct 18, 2024

    same quetion

    pretty_pixels
    Author
    Oct 18, 2024

    Better prompt understanding than Schnell while practically losing nothing in speed (still 4-step).

    WanderlustaiSep 27, 2024
    CivitAI

    Is there a Workflow I can find for this one?

    pretty_pixels
    Author
    Sep 28, 2024

    The demo images were made in Comfy so you can just drag and drop to get the workflow

    YellowbootOct 3, 2024
    CivitAI

    Yes, the model is fast, but still significantly worse than full Flux.dev

    SyamsQOct 18, 2024

    what gpu did you use?

    YellowbootOct 18, 2024

    @SyamsQ 12GB

    SyamsQOct 19, 2024

    @Yellowboot RTX 4070Ti?

    YellowbootOct 19, 2024

    @SyamsQ 3060

    SyamsQOct 20, 2024

    @Yellowboot How fast does your PC generate a single 1024x1024 image?

    YellowbootOct 20, 2024

    @SyamsQ quality is more important to me than speed

    TheSilentFoxDec 16, 2024
    CivitAI

    Is there a ComfyUI workflow that can utilise this Q8 v2 that you would recommend? my current ones can't find it?

    pretty_pixels
    Author
    Dec 17, 2024

    Make sure have the extension https://github.com/city96/ComfyUI-GGUF . See the images of Q4_0 for workflow, swap out the model for Q8_0

    ApexArtist1Jan 5, 2025
    CivitAI

    Unet or checkpoint folder

    pretty_pixels
    Author
    Jan 5, 2025

    Unets. (BTW, make sure to unzip the file first.)

    sara4funJan 10, 2025
    CivitAI

    after downloading 2 times it says archive is corupt

    pretty_pixels
    Author
    Jan 10, 2025

    I can assure you that there are no problems with the upload, either it's something on your end or CivitAi servers suddenly acting up or something.

    sara4funJan 10, 2025

    @pretty_pixels ok thanks for responding, ill give i download again. Great work. really

    remag77777777211Apr 24, 2025
    CivitAI

    Can the images created by this neural network be sold? I really don't understand the point of all these licences.....

    xenoformJul 23, 2025
    CivitAI

    This is a truly amazing achievement - this merge.
    It maintains much better anatomy and composition, outputs much closer to Dev than Schnell.
    My sincere congratulations, and thank you very much!

    darthjawn546Jan 24, 2026
    CivitAI

    https://youtu.be/eVgRxWEitFw

    Thanks you Black Forest Labs! Greats tools and I made this.... "Neon Fugue". A nostalgic trip to the hardboiled neo-noir police movies of the late 1970's with funky music and no nonsense crime busting.

    Checkpoint
    Flux.1 S

    Details

    Downloads
    472
    Platform
    CivitAI
    Platform Status
    Available
    Created
    8/20/2024
    Updated
    5/12/2026
    Deleted
    -

    Files

    ggufFastfluxFlux1Schnell_q50V2.zip

    Mirrors

    Available On (1 platform)

    Same model published on other platforms. May have additional downloads or version variants.