If SingleFile shows “This page cannot be saved with SingleFile,” first check whether the page is an ordinary website, a browser-restricted domain, or Firefox Reader View. Those cases have different causes, and the available evidence does not establish that SingleFileZ is the same product as SingleFile. The Firefox permission workaround below applies only to a specific support.mozilla.org case; it is not a universal fix.
First, identify what you are trying to save
Note the browser, the exact address, and whether the page is displayed as a normal website or in a browser-generated view. Also distinguish a save that fails entirely from a saved file that opens but is missing content.
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- Ordinary website: Check for an extension update if the failure affects only a particular site.
- Browser-owned domain: A browser may restrict extension content scripts on domains it owns. A SingleFile maintainer described this cause for one Firefox support.mozilla.org report.
- Firefox Reader View: A 2019 report associates Reader View with the same message, but does not document a confirmed fix.
- Incomplete saved page: If the file was created but lacks older or off-screen content, the site may be removing that content from the page as you scroll. That is a different problem from extension permissions.
The evidence here concerns SingleFile. It does not verify whether SingleFileZ is a separate product or another name for SingleFile, so do not assume the settings or fixes below apply to SingleFileZ. Check the extension’s publisher and documentation before changing browser settings.
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For a report involving support.mozilla.org, SingleFile maintainer Gildas Lormeau said on February 1, 2021 that browser providers block extension content scripts on some domains they own. His case-specific workaround was to remove support.mozilla.org from Firefox’s extensions.webextensions.restrictedDomains preference in about:config.
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- In Firefox’s address bar, open
about:config. - Accept the warning if Firefox displays one. This is an advanced settings page; change only the preference described here.
- Search for
extensions.webextensions.restrictedDomains. - If the preference contains
support.mozilla.org, remove only that domain from its value. Preserve other entries and the value’s existing format. - Retry saving the page. If the preference does not contain that domain, do not add or remove unrelated entries as a speculative fix.
This is a historical, domain-specific maintainer response, not a guarantee that the preference is present or that changing it will work in current Firefox. The same discussion includes a later report that clearing the preference did not fix a problem on addons.mozilla.org. If the setting is absent, the error persists, or you are unsure how to edit the value safely, restore the original value if you changed it and consult current Firefox and extension documentation.
Firefox Reader View is a separate case
A SingleFile issue report from August 2019 describes the message while saving Firefox Reader View. The report used Firefox Quantum 68.0.1 on Windows 10; it is evidence of that historical observation, not current compatibility documentation, and it does not establish a confirmed remedy.
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As a practical diagnostic, try saving the ordinary page rather than its Reader View rendering. If only Reader View fails, treat it as a browser-generated-view issue rather than assuming the Mozilla-domain preference is relevant. The report does not establish that this test will resolve the problem.
Check for a page-specific save bug and update
If the failure is limited to one site and neither a browser restriction nor Reader View fits, check whether SingleFile has an update. Mozilla’s Firefox Add-ons version history listed SingleFile 1.26.4, released September 23, 2026, with a fix for saving some pages, including Substack home pages. That note indicates a page-specific bug fix; it does not mean every “cannot be saved” message is caused by an outdated version.
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Open the SingleFile version history for the current release information, since versions and release notes change. If you already have the latest version, note the affected URL, browser and version, and whether the page is a browser-generated view when reporting the issue to the extension’s maintainers.
If the file saves but content is missing
Some sites virtualize long pages: they remove off-screen items from the document and insert other items as you scroll. A saver cannot capture messages that are no longer present in the page. SingleFile’s guidance for AI chat conversations describes ways to expose more content before saving, including increasing the browser window height (the extension’s zoom-out approach) and using its user-script method for supported embedded scroll areas. A window height that is too small can still leave content out.
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The wiki gives one author-reported example, not a general benchmark: on an X thread with 252 replies, the author saved 19 replies at the default window height, 141 at 4,000 pixels, 249 at 8,000 pixels and 252 at 16,000 pixels; the 8,000-pixel save was reported as a 7.6 MB file. Results will depend on the page and setup. Larger captures can create much larger files, so verify the saved page and its size rather than assuming a partial result is complete.
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For a clean screenshot rather than a SingleFile archive, ScreenshotNeo provides a one-request API. It accepts consent banners like a visitor and removes more than 60 known consent platforms, newsletter popups and chat widgets before capture; each step can be turned off. Bot checks, blank pages, timeouts, failed loads and cache hits are not billed, and the response identifies the page verdict and billing status in headers. Its MCP server also lets AI agents use take_screenshot, get_page_info and capture_pdf. This is a screenshot/PDF alternative, not a way to produce a SingleFile HTML archive.
For example, use cURL to save a WebP screenshot of a page:
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