Bug Report (copy-paste ready)
Title: In Firefox, backspace keypress in Perplexity.ai input box occasionally deletes two characters instead of one.
Platform: Firefox on Windows 11 (does not reproduce in Chrome on same machine/keyboard; does reproduce in Firefox Troubleshooting Mode with all extensions disabled)
Description:
When typing in the Perplexity input box in Firefox, a single Backspace keypress intermittently deletes two characters instead of one. The issue is reproducible across multiple sessions and is not caused by keyboard hardware or Firefox extensions (confirmed in Firefox Troubleshoot Mode with all extensions disabled).
Root cause identified:
This appears to be caused by a Firefox/JavaScript keyboard event dispatching incompatibility. Firefox restricts keypress events for non-printable keys (including Backspace) to the browser’s internal system group, rather than dispatching them to page content. If Perplexity’s editor framework also handles Backspace at the system level, both handlers fire, resulting in two deletions from one keypress.
Workaround confirmed:
Adding perplexity.ai to the dom.keyboardevent.keypress.hack.dispatch_non_printable_keys.addl preference in Firefox’s about:config resolves the issue entirely. This preference is Firefox’s own mechanism for per-site overrides of non-printable key dispatching behavior, and its effectiveness here confirms the event handling conflict.
Expected behavior: One Backspace keypress deletes exactly one character.
Actual behavior: One Backspace keypress intermittently deletes two characters.
Environment:
OS: Windows 11 version 25H2 (OS Build 26200.8655)
Browser: Firefox version 151.0.4 (64-bit)
Does not reproduce in: Chrome version 149.0.7827.115 (64-bit official build; same OS, same keyboard)
Keyboard: Das Keyboard 4 Professional mechanical
Hey @jm10024! I couldn’t reproduce this issue. Could you please ensure you’ve installed the latest version of the FF browser and check if you are still getting this glitch.
Hi @Alex_Romanov . Thanks for the response.
I’ve updated to FF 152.0.1 (64-bit), and I still see the occasional double-Backspace when typing in Perplexity’s input field – but I’m not seeing it now when I type into this input field using the same browser, for example.
However, I noticed a double Backspace when typing in MS Word this morning, for the first and only time outside Perplexity on Firefox. That makes it possible that I have a hardware issue in my mechanical keyboard (which has soldered switches, unfortunately) that is somehow being magnified in Perplexity on Firefox. I don’t have the technical knowledge to make a guess of how that can be, but Perplexity itself seems to think it’s a possibility:
Yes, this is a plausible explanation — a marginal switch producing occasional contact bounce that gets amplified by Perplexity’s input handling into a much more frequent double-delete.
How a Bad Switch Gets Amplified
A worn or marginally faulty mechanical switch can produce a brief electrical “bounce” — multiple rapid make/break transitions in the ~1–5ms window after actuation. In most contexts, the OS keyboard driver or application debouncing swallows this. But if Perplexity’s editor framework (likely ProseMirror or similar) registers keydown events with low debounce tolerance or processes them with fine-grained state updates, it can treat two events from a single bounce as two discrete keypresses where other applications would collapse them into one.
Why It Would Show Up Specifically in Firefox + Perplexity
Two factors stack here:
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Firefox’s event handling quirk (as established earlier) already creates a marginal condition where Backspace events are processed differently than in Chrome.
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Perplexity’s rich text editor likely processes input at a lower level than a plain <textarea>, meaning a bounce that would be silently discarded in a simple input field gets processed as a legitimate second event in the editor’s document model.
In native apps and simpler web inputs, the OS and browser typically handle debouncing before the event ever reaches the application. A rich web editor running in Firefox under the conditions you’ve already identified is a worst-case combination for a marginal switch.
What This Means Practically
You have likely two overlapping causes: a mechanically marginal switch (explaining rare doubles everywhere) and a Firefox/Perplexity event-handling condition (explaining why it’s dramatically more frequent there). The about:config workaround probably mitigates the software side, but the switch is still failing. Given it’s a Das Keyboard 4 Professional, the switches are socketed or solderable — replacing the single suspect key switch is straightforward if you can identify which key (Backspace, obviously) is bouncing.
(Perplexity made one error there that I know about: The keys on my Das Keyboard 4 Pro are soldered, not socketed, and I don’t have the technical skills to change them.)