2026 年 AI 圖像放大工具比較：本地模型與線上工具

Originally published on AI Stack Lab: https://aistacklab2026.blogspot.com/2026/10/best-ai-image-upscalers-in-2026-local.html

If you search for the best AI image upscaler, most results promise "4x more detail" and never mention the awkward part: an upscaler cannot recover detail that was never captured. It guesses. Sometimes the guess is excellent, and sometimes it paints a confident wrong eyelash or a smooth, plastic-looking wall. This guide compares two free local options with three online or hybrid tools, and keeps that distinction front and center. I read each vendor's own page on October 25, 2026 for prices, limits, and scale factors. I did not run a benchmark, measure sharpness scores, or compare outputs side by side, so I make no quality-ranking claims. Where a number was unclear or missing, I say so.

The 30-second answer

• Best free, no sign up: Upscale.media. Its page says you can upscale one image per day without signing up. It is a fine fit for a one-off image.
• Best local / open-source: Upscayl. It is listed as free and open source, with desktop apps for Linux, macOS, and Windows. Real-ESRGAN is the engine-level choice if you want command-line control.
• Best paid tool for professionals: Topaz Gigapixel. It is subscription-only, but it offers local rendering, so your files can stay on your machine.
• Best for illustration and anime art: Bigjpg offers an "Artwork" mode, and Real-ESRGAN ships anime-specific models. For faces, Real-ESRGAN's optional GFPGAN face enhancement exists, but see the caveat below.

These are picks from published specs and project documentation, not from my own side-by-side testing.

How I compared them

I used five criteria:

• True detail recovery vs hallucinated detail: does the tool reconstruct what was probably there, or invent plausible texture? I cannot rank this without testing, so I describe the model type and the risk instead.
• Max upscale factor: as published, free versus paid.
• Batch and local processing: can you process a folder without uploading it anywhere?
• File size and privacy: upload limits, and whether the image leaves your machine.
• Price: free tier and paid plans, with the date checked.

One honest limit: bigger numbers on a landing page are marketing. Topaz's own page is inconsistent, saying "up to 16x pixels" in a description and "6x" in a headline. Treat the scale factor as a ceiling, not as a promise of quality.

Comparison table

Prices checked October 25, 2026, in USD, as published. Vendors change pricing often, so confirm on the pricing page before you buy.

I did not check Adobe's, Canva's, or Photoshop's built-in upscalers, or any ComfyUI diffusion-based workflow, so I have not rated them.

Deep dives

Upscayl: the best local starting point

Upscayl's site describes it as free and open source, with desktop builds for Linux, macOS, and Windows and a maximum scale of 16x. It offers multiple models for different needs, though the page does not name them. A cloud option exists with its own pricing link, but I could not see prices, so I am not quoting any. It is the one I would install first because there is no account and nothing to upload.

Verdict: the easiest way to try local upscaling without touching a terminal. Catch: I did not verify its hardware requirements, and a very large factor like 16x will be mostly invention, whatever the tool.

Real-ESRGAN: the engine behind a lot of free tools

Real-ESRGAN is a research project for general image and video restoration, trained on synthetic degradation. Its repo lists the BSD-3-Clause licence, a main x4 model, and portable executables for Windows, Linux, and macOS that work with Intel, AMD, and Nvidia GPUs without a CUDA or PyTorch install. For illustration, it ships an anime-specific model. For portraits, an optional flag runs GFPGAN face enhancement, which needs two extra Python packages.

Verdict: best if you want scripting, batch folders, and no UI. Catch: the repo publishes no VRAM figures, and the portable build does not support every feature, such as the custom output-size option.

Topaz Gigapixel: the paid local option

Topaz sells Gigapixel on subscription only. Personal is $29 monthly or $149 on an annual plan, and Pro is $499 annually, with "full commercial use" on Pro and "limited commercial use" for organizations under $1M revenue on Personal. The page advertises unlimited local and cloud rendering, and says local rendering keeps files on your computer.

Verdict: worth it only if you upscale for paid work regularly and want one supported app. Catch: no free trial appeared on the page I read, and I did not test it against the free tools, so I cannot say it looks better.

Upscale.media: the quick online option

Upscale.media's own text says that without signing up you can upscale one image a day for free, and that signing up is required for bulk work. Credit packs run from $7.99 for 60 credits up to $54.99 for 1,200.

Verdict: good for the occasional single image when you do not want to install anything. Catch: the maximum scale and resolution are not stated on the page, so check before you rely on it for print.

Bigjpg: the artwork-focused online option

Bigjpg offers an Artwork or Photo mode, which matters because anime and line art behave differently from photographs. The free plan allows 20 pictures a month at up to 4x, with a 5MB limit. Paid plans start at $6 for two months, and add batch mode, 50MB uploads, and 8x and 16x.

Verdict: a sensible stop for illustrators with the occasional image. Catch: I could not confirm whether free use needs an account, and the page does not name its underlying models.

Local models vs online tools

Privacy: your images on someone's GPU

An online upscaler means your file goes to someone else's server. For holiday photos that is probably fine. For client work, unreleased product shots, or anything with identifiable faces of other people, read the vendor's retention policy first. I did not review retention policies for these tools. Local tools avoid the question: Upscayl and Real-ESRGAN process files on your machine, and Topaz says its local rendering keeps files on your computer.

Batch workflows

Online free tiers throttle you. Bigjpg's free plan is 20 pictures a month and explicitly excludes batch, and Upscale.media's no-sign-up route is one image a day. If you have a folder of 500 scans, local is the practical answer, and Real-ESRGAN's command line suits scripting.

Hardware: the VRAM reality check

Here is where I have to be careful. None of the pages I read published minimum VRAM figures, and I did not run these tools, so I will not invent any. What I can say: Real-ESRGAN offers a tiling option that processes the image in pieces, which exists precisely because large images strain GPU memory, and the cost is possible visible seams. If your GPU is weak, expect either tiling artifacts or slow CPU fallback. If you already think about local GPU limits for language models, our guide to running LLMs locally covers the same trade-offs.

Real detail or invented detail?

This is the part marketing skips. Upscalers like these are trained neural networks that add plausible texture. On a low-resolution photo, that can look sharp and wrong, such as a face that no longer resembles the person. Text is the classic failure: letters can become convincing-looking nonsense. Line art and anime usually tolerate upscaling better because edges are simple, which is why artwork-specific modes exist. A 2x increase is a modest guess; a 4x or 16x increase means most of the new pixels are invented. That is a general property of this approach and not a measurement from my own tests.

When free online tools are genuinely fine

A single social-media image, a blog thumbnail, a casual wallpaper, or a quick look at whether an old picture is salvageable. If the image is not sensitive and you need one result, a free no-sign-up tool is fine.

Who this is NOT for

• Forensic, legal, or medical image work. Invented pixels are not evidence. Do not use any upscaler to "enhance" an image you need to treat as factual.
• People who need to recover small text. I have not tested text recovery, and the risk of plausible-looking wrong letters is real. Re-scan or re-photograph the source.
• Anyone wanting benchmark rankings. I ran no tests and do not publish PSNR, SSIM, or similar scores. Try two tools on your own image.
• Buyers of AI-generated image workflows. I did not evaluate diffusion-based upscalers or built-in upscalers in Adobe, Canva, or ComfyUI.
• People with no discrete GPU who want big batches. Hardware needs are unverified here, so test a small batch before committing a weekend.

Final recommendation

Start free and local: install Upscayl, run your image at 2x first, and compare it with the original at 100% zoom. Use Real-ESRGAN if you want scripting and anime models. Use a free no-sign-up online tool such as Upscale.media for a one-off, non-sensitive image. Consider Topaz Gigapixel only if upscaling is part of paid work. Whatever you choose, keep the original file, and treat anything above roughly 2x to 4x as a creative guess rather than a recovery.

Keep reading

• Best AI Image Generators Compared
• Run LLMs Locally in 2026: Ollama vs LM Studio vs llama.cpp, Compared

Spotted an outdated price or want a tool added? Email nandminc2020@gmail.com.