The Comment LINK line in Facebook captions
A line at the start or end of Facebook (and, with their own switch, Instagram) captions telling viewers what to comment to get your Auto DM.
When Auto DM is available, Settings → Auto DM has a switch labeled Add "Comment LINK" to captions when Auto DM is on, at the bottom of its Facebook card, on by default. The switch saves by itself; a changed wording under it, Wording of that line, is saved with Save changes in the bar at the bottom of the page.
What it does
The word people are asked to type can differ from post to post, so it can be targeted to a product: the line uses your first trigger word (or the word you chose to show, below), or the post's own first trigger word when that post (or its product) has its own Auto DM words. Facebook captions get a line like Comment LINK and I'll send you the link 👇 — using that word in upper case — whenever Auto DM is on and the post has something to sell. That includes a TikTok Shop video whose Amazon product isn't matched yet: captions can't be changed after posting, so the line is ready for when the product is. Turn the switch off to stop adding the line, or change its wording below it. The line under the box, People will read, shows the result with your first trigger word (or the word you chose to show) in upper case. Your own wording must keep the trigger word exactly once, spelled {{word}} (the + Trigger word button puts it in at the cursor), hold no link, and stay under 120 characters. A line you saved earlier with {word} still works: the box shows it as {{word}}, and saving it stores the new spelling — the link itself always goes in the DM, not in the caption.
If people comment before the video has a link
The line goes into the caption when the post goes out, so it can be there before the video has a product. A comment with your trigger word that arrives while the video has no Amazon product to send gets no DM, and it isn't sent later. Choose a product (or give your DM its other buttons) and the next comments get their DM; see Auto DM isn't sending. The same goes for a post whose match to a TikTok video isn't confirmed yet: once you confirm it, the next comments get their DM.
Choosing the word it shows
Where it's available on your account, Settings → Auto DM has Show this word in your captions under your trigger words: one button per word that's on, like LINK, SHOP and INFO. Pick SHOP and captions say Comment SHOP, while LINK and every other trigger word still get the DM, so you never have to turn LINK off to keep it out of your captions. The pick is saved with Save changes, covers Facebook and Instagram (Instagram with its own words uses it when it's one of them, otherwise its own first word), and a post with its own Auto DM words still names that post's own word. If you later turn the chosen word off, captions go back to your first trigger word and the editor says so; turn it back on and your pick returns. In setup, typing your own line with another of your trigger words, like Comment SHOP for the link, offers Show SHOP instead: one tap and that line is used. Until you tap, the caption step keeps showing the word your captions use now.
Start or end of the caption
Under the switch, Where it goes has two choices: Start of caption (the default) and End of caption. It saves the moment you press it and covers both Facebook and Instagram. At the start, the line opens the caption, then a blank line, then your caption. At the end, it comes after your own text and before the hashtags that end your caption, so the line isn't buried under them; a #ad at the very end stays with those hashtags. Your Amazon link line still comes last on Facebook. The choice shows only while the line is on. In the mobile app it's in Settings, in the Facebook Auto DM block (Where “Comment LINK” goes) and under Instagram's caption line.
When your Auto DM language is Español (where Spanish is on for your account; see Auto DM), the ready-made line is Spanish instead: Comenta ENLACE y te envío el enlace 👇. A line you wrote yourself stays as you wrote it.
Your caption stays whole, whichever place you choose. Under the caption box in the Composer (and on a post's card in the mobile app) one short line reads First line on Facebook and Instagram: and the line (Added after your text on when you chose the end), or says there is no Auto DM line and why, with Change to open this setting. When Facebook and Instagram differ, or the DM can't send yet, See each platform (Details for one platform) opens a sentence per platform with the reason, for example No product on this post yet: add one so the DM has a link to send. The note updates as soon as you save your own link or Auto DM setting for that video, so "no Auto DM line" goes away once the video has a link to send, without reloading the page.
When it's left out
The line is skipped when your caption already asks people to comment a trigger word, or when there's no room left in the caption.
It is also skipped when your caption asks for a word of its own, like Comment NECK for the link (or two or three words in upper case or in quotes, like Comment TRUCK TILES and I'll send you the link), and Auto DM answers that word (the Also answer the word each post asks for choice, where it is available on your account), so the post never asks for two different words. The note under the caption box then reads that your caption already asks for that word and that its comments get the DM, or, when the DM can't send yet (for example no product on the post), says why. Where Auto DM would not answer your caption's own word, the line is still added, so comments with your trigger word still get the link.
It is also left off a post that has nothing to sell: a video that isn't a TikTok Shop video and has no Amazon product or link of your own on it, or a video you marked Not on Amazon without giving it your own link. That post goes out with your caption exactly as written, unless your Auto DM has Buttons in your DM (where that's available, see Auto DM) with a button 2 or 3 of your own (Custom) set: then the DM still sends that link, so the line stays. My TikTok video alone keeps the line only on a video marked Not on Amazon (a TikTok Shop video you sell there, say), because whoever comments gets the DM with the TikTok button. On a video that isn't a TikTok Shop video and has no product, My TikTok video alone doesn't count, because it only points back to the same video: such a post still gets no line, though anyone who comments your trigger word still gets the DM with the TikTok button. With Button 2 set to None (or when we can't tell which TikTok video the post came from), nothing would be sent, so there's no line. Add a product or your own link before it posts and the line comes back. The note under the caption box says which it will be.
It's added to the finished caption after any caption cleanup and before your Amazon link line: at the start of the caption, or, with End of caption, after your text and before your closing hashtags (then #ad, when it's added, and the link). There's no room for it when the caption with the line would pass 1,000 characters; then the caption posts as written, with your link and #ad as usual.
Leave it off one post?
Where it's available on your account, the note under a post's caption box in the Composer (and on the post's card in the mobile app) has Leave off this post next to the line. Press it and that one video's Facebook and Instagram captions go out without the line; the note then reads that the Auto DM line is left off this post, and Add it back puts it back. It saves the moment you press it, and covers Post now, a scheduled post and an automatic post of that video. A scheduled Facebook or Instagram post has the same choice under Will post as when you edit its caption. Auto DM still works on that post: anyone who comments your trigger word still gets the DM (when it can't send yet, for example no product on the post, the note says why); only the line telling them to is left off. The switch in Settings still covers all your other posts.
Where it isn't available yet, there's no switch to leave it off one post: the switch above covers all your posts. Either way, a post with nothing to sell is left without the line on its own (see When it's left out, above), and a caption that already asks for a word keeps just that one.
On Instagram
The Instagram card in Settings → Auto DM has its own choice under Caption line, Add "Comment LINK" to Instagram captions (it names your first trigger word, or the word you chose to show, in upper case, LINK being the usual one), using the same wording and the same place (start or end). The line goes on an Instagram caption as soon as you switch on Auto DM on Instagram, even before it can send, so your posts are ready the day it starts. While it can't send, people who comment on Instagram don't get a DM, and the note under your caption says why. For example Reconnect Facebook so Auto DM can send. means your Facebook connection is older than Meta's approval of Instagram comments: reconnect Facebook once. It never holds a link: Instagram captions can't.
In setup, the caption step has one switch for this line that names whichever platforms have Auto DM on (for example Start Facebook and Instagram captions with “Comment LINK”); turning it off there stops the line on both. Instagram's line follows Instagram's own Auto DM switch, never Facebook's.