The best free, open source NSFW image blocker
If you want one answer: NSFW Filter is the only image blocker in its class that is free forever, fully open source, and runs entirely on your device. That combination is the point of this comparison, so the rest of this post explains what the alternatives do differently and when one of them is the better fit. No tool wins every row, and a couple of the popular ones are not really solving the same problem.
Two different jobs share one keyword
Search for a way to block adult content and you get two kinds of tool mixed together.
One kind blocks whole sites. You give it a blocklist or a DNS service, and requests to known adult domains fail. BlockerX, CleanBrowsing, and Covenant Eyes live here. They are built for parental control and for people in recovery who want a site gone and hard to turn back on.
The other kind looks at images. It runs a classifier over the pictures on whatever page you are on and hides the explicit ones, regardless of the domain. NSFW Filter, HaramBlur, and NSFWBlur live here. This is the tool you want when an explicit image can show up anywhere, in a feed, a search result, an embed, and you want it caught before you see it.
They are not competitors so much as different layers. A site blocker cannot judge one image on an allowed domain. An image blocker does not take a whole site offline. Plenty of people run one of each.
The comparison
This table covers image-level tools alongside a couple of common site-level and built-in options, so the distinction above is visible. Features change, so treat it as a starting point and verify anything that matters to you.
| Tool | Free | Open source | On-device | Blurs images | Full-site block | Account | Adjustable effect |
|---|---|---|---|---|---|---|---|
| NSFW Filter | Yes | Yes | Yes | Yes | No | No | Yes (blur / grayscale / hide) |
| HaramBlur | Yes | Yes | Yes | Yes | No | No | Partial |
| NSFWBlur | Freemium | No | Yes | Yes | No | Varies | Partial |
| BlockerX | Freemium | No | No | No | Yes | Yes | n/a |
| Covenant Eyes | Paid | No | No | No | Yes (+ monitoring) | Yes | n/a |
| Google SafeSearch | Yes | No | No | Search only | No | No | No |
Why open source matters here
Every tool in the image-blurring category says it runs locally and keeps your data private. That is easy to write and impossible to verify when the code is closed. “On-device” is a claim; open source is proof.
NSFW Filter’s code is on GitHub . You, or anyone you ask, can read exactly what it does with the images it sees, which is: classify them in your browser and nothing else. For a tool whose entire promise is privacy, being auditable is not a nice-to-have. It is the difference between trusting a marketing line and checking the receipt. HaramBlur deserves credit here too; it is also open source and on-device, and if its behavior fits you better, use it.
Honest scope
NSFW Filter blurs, grayscales, or hides explicit images. It reads static images, not video. It does not block whole sites, and it is not an accountability tool that reports to another person. If what you need is a site-level block with a password and uninstall protection for recovery, a dedicated blocker is the right tool, and NSFW Filter is a good free layer to run alongside it. We go into that in the free alternative to BlockerX and Covenant Eyes .
If your goal is explicit images blurred everywhere, on any site, with nothing leaving your machine, that is exactly what this is built for. Read how the on-device classifier works , or just install it.
Frequently asked questions
Is there a free, open source NSFW image blocker?
Yes. NSFW Filter is free, open source, and runs entirely on your device. It blurs, grayscales, or hides explicit images on any website using an AI model bundled in the extension, with no account and no data collection. The source is on GitHub.
What is the difference between an image blocker and a site blocker?
An image blocker like NSFW Filter looks at the actual images on a page and hides the explicit ones, on any site. A site blocker like BlockerX or CleanBrowsing blocks whole domains by URL or DNS. Site blockers cannot judge an individual image; image blockers do not block whole sites.
Which NSFW blocker is best for privacy?
One that classifies images on your device and sends nothing to a server. NSFW Filter does this and is open source, so you can verify the claim. Cloud-based or accountability-based tools by design send some record of your activity off your machine.