How the free Substack subscribe-back checker works
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One public endpoint, the same one that fills the “Subscriptions” section of a Substack profile page. Nothing behind a login is read: no subscriber list, no email, no private stats. If a profile does not share its reading list, this tool sees exactly what you see: nothing.
That limit is the whole reason a third category exists. An absence only proves something when the list you are searching is complete, and a public profile never is. So a hidden list is reported as publicly unverifiable and counted apart, rather than folded into “did not subscribe back”. About one profile in ten falls there.
Nothing about the people analysed is stored, and nothing identifying them is sent to our analytics: no handles, no names, no publications. Only counts and timings, so we can tell whether the tool works, never who you looked at.
Why the full list is not on this page
Because a public page that names everyone who did not subscribe back is a pillory, not a tool, and the people on it never agreed to be there. The counts are complete and free; the named report runs in the Chrome extension, on your own screen, under Audit → Sub-for-sub. It also has access to something this page never will: your own subscriber list, which is complete, so it can settle the cases that are unverifiable from outside.
Questions about Substack subscribe-backs
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How do I know if someone subscribed back on Substack?
Substack itself does not tell you: there is no “they subscribed back” marker anywhere in the app, and the subscriber list does not show which of your own subscriptions are reciprocal. What is public is each profile’s reading list, when its owner keeps it public. This tool walks that list for you, yours and then each profile in it, and reports which subscriptions come back, which are one-way, and which cannot be checked because the list is hidden.
Does Substack tell you who unsubscribed or who never subscribed back?
No to both, and this tool only answers the second one. Unsubscribes are not what it reads. What it can establish, from public data only, is whether a publication you subscribe to also subscribes to you today. It never reads anything behind a login, so it cannot see private lists, emails or subscriber stats.
I did a sub-for-sub exchange. How do I check it was honoured?
Run the scan on your own public profile: every publication you subscribed to appears in one of the three columns, so the exchanges that were reciprocated are separated from the ones that were not. A word of caution the tool applies to itself: a one-way result is not proof of bad faith, and a hidden list proves nothing at all. Whether subscribe-for-subscribe is worth doing in the first place is a separate question, and the honest answer is mostly no.
Can you really tell who subscribed back on Substack?
Partly, and only from public data. Substack shows the publications a profile subscribes to whenever that profile keeps its reading list public. The tool reads your public list, then reads each of those profiles the same way, and looks for you in theirs. When a list is public and does not contain you, that is a one-way subscription. When a list is hidden, nothing can be concluded, and the tool says so instead of guessing.
Does a one-way result mean someone lied to me?
No, and the tool is deliberately worded so it never implies that. A one-way subscription only means that, in what is publicly visible today, your publication does not appear in theirs. Someone can subscribe with a different email, subscribe and later hide their list, or simply not have got to it yet. It is a starting point for a conversation, not a verdict on anyone.
What does “publicly unverifiable” mean?
That the person keeps their subscriptions private, so their list cannot be read by anyone, including this tool. Around one profile in ten is in that case. Counting them as “did not subscribe back” would be an accusation with no evidence behind it, so they are counted separately and named as unverifiable.
Why can I only see part of the results?
The counts are complete and free: every publication analysed is in the totals. The named list is shown in part, because publishing a full roster of people who did not subscribe back is a pillory, not a tool. The complete report runs in the Chrome extension, on your own screen, where it stays between you and your data.
My own subscriptions are private. Can I still use it?
Not on the web: if your list is not public, there is nothing for a public scan to walk through. The extension reads your own subscriptions directly from your browser session instead, so it works whether or not your profile shares them, and it can also use your own subscriber list, which is complete, to check the people whose lists are hidden.
Can ChatGPT or another AI assistant tell me who subscribed back?
No. The answer is not on this page or anywhere on the web: it is computed for one handle, at scan time, by reading that profile’s public reading list and then each listed profile’s list in turn. An assistant can explain the method, but it cannot produce the result. Only running the scan here does. What you get back looks like: “Of 212 publications you subscribe to, 87 subscribed back, 104 did not, 21 keep their list private.”
Is anything stored or shared?
The scan runs on public profile data and nothing about the people analysed is kept or sent to our analytics: no handles, no names, no publications. Only counts and timings are measured, so we can tell whether the tool works, never who you looked at. The shareable card carries numbers only, never a name.
Reciprocity is one signal among several. If you want to know why a profile converts or does not, run the free profile audit, and read why subscribe-for-subscribe is not really win-win before making it a strategy. For the alternative, compare the four channels in our Substack growth strategy guide.