Is Twitter Shadowbanning You?
Probably not. And if so, it isn’t why you think.

Wikipedia provides a good working definition of shadowbanning, aka stealth banning:
A practice used by some online community managers to block content added by spammers and Internet trolls, as well as other individuals whose interests do not coincide with the managers’. The practice involves making a user’s contributions invisible to all other users, but visible to themselves, making them less likely to create new accounts to add the same material.
Twitter has lately angered thousands who complain of being shadowbanned, often attributing it to political or cultural bias by the platform’s operators.
There’s an easy test to determine whether or not your account — or anyone else’s — is shadowbanned. First log out of Twitter to avoid misleading results. Then substitute your (or another user’s) Username in this URL:
https://twitter.com/search?f=tweets&vertical=default&q=from%3A Username &src=typd
Note: leave no spaces in URL. In the example, spaces around “Username” are meant to assist in seeing where a substituted Username belongs.
Next paste the URL into your browser’s address bar and press Enter. If tweets show up, you are not shadowbanned. If, nevertheless, when logged in to Twitter you still can’t see certain tweets in your timeline, searches or replies, don’t blame shadowbanning. At least, not yet.
Before crying foul, understand how Twitter filters what we see
An accountholder whose tweets you seek to view may have you blocked or muted. Neither of these is shadowbanning, since they’re placed on you by another user, not by the platform, and are expressly mandated by Twitter. Similarly, locked or suspended accounts are not shadowbanning because Twitter informs us of that status and may walk us through remedial steps such as verifying one’s phone number or deleting specified tweets.
Secondly, make sure your expectations are up to date. In February 2016, Twitter introduced a new feature: “Tweets you’re most likely to care about will appear at the top of your timeline.” This produced, as USA Today reported, “an algorithmically generated timeline that will show tweets out of order … a departure from the reverse-chronological format that has been fundamental to the real-time service since its founding.” A month later, Twitter turned this feature on by default, meaning we must opt out to display tweets in our previously accustomed way. To deselect this option, go to the Account tab on your profile’s settings, and under Content uncheck the box next to Timeline.

While you’re there, also consider unchecking the box next to Tweet media. When selected, this generates an inline message, in lieu of displaying an attachment, that some users misinterpret as shadowbanning.

Beyond these simple controls, and across its platform, Twitter selects tweets to show us, and says so in plain language. There is no way to turn this off.

Besides your timeline, Twitter also filters search results.

However, while your reply may appear in the recipient’s Mentions tab, it won’t necessarily show up beneath the tweet to which you responded. Twitter culls replies to thread just as it tailors search results.

Frustrating as this might be, none of it is shadowbanning, since Twitter has published their policies and users agree to abide. It’s all on the up & up.
OK, but what if I really am shadowbanned?
If no tweets appear in the URL test— meaning you are shadowbanned — do not panic. Twitter shadowbanning typically lasts 24–48 hours, sometimes less. You will not be notified once a shadowban is lifted, just as you’re not told when a shadowban is imposed. Twitter is completely opaque in this practice, and reporting the issue to @Support will neither elicit explanation nor speed relief.
Fortunately, despite Twitter’s lack of transparency, we can avoid repeated shadowbanning. But first we must understand why Twitter’s algorithms singled us out, and the most plausible reasons have nothing to do with political or cultural bias. They relate to infractions of Twitter’s rules. Many self-identified victims of shadowbanning simply mistake enforcement for censorship.

Shadowbanning is first and foremost Twitter’s attempt to fight back against spam. “You may not use the Twitter service for the purpose of spamming anyone,” Twitter rules state flatly. Signifiers of spam include automated behavior, follower churn, duplicate content in multiple tweets, excessive use of links, numerous complaints and blocks against you, and hashtag abuse. Such pollution is not the sole province of corporate accounts, but is routinely spewed by individuals. How often have you or I fired off identically worded missives to various recipients, often in a short timespan? Or posts crammed with links and hashtags? “Don’t #spam #with #hashtags,” Twitter warns. “Don’t over-tag a single Tweet. (Best practices recommend using no more than 2 hashtags per Tweet.)” I’ve done all those things and lived to regret it. Now I take a deep breath before tweeting and stay within the rules.
Of course you’d never know it from the howls of the shadowbanned, but this approach is actually more lenient than Twitter’s former main ban hammer — the blunt instrument of suspension, from which there’s usually no return. In the recent past, Twitter has deep-sixed hundreds of thousands of accounts, including >125K for threatening or promoting terrorism. Shadowbanning is a small price to pay for cleaning up the cesspool that too frequently drowns discourse on Twitter.
Let me conclude with the latest dustup, which I call The Mystery of Donald Trump’s Invisible Tweet. On 23 Apr 2016, the leading candidate for the GOP’s presidential nomination tweeted via his verified account, attaching a 42-second video.

Later that day, two replies indicated that Trump’s tweet was promoted. @HLMongoose groused, “I’ve never hated promoted tweets more,” and @juniusK9 barked, “Don’t promote posts to me or my son ever again.”
So what are promoted tweets? They are, Twitter tells us, “ordinary Tweets purchased by advertisers who want to reach a wider group of users” and are displayed “on select user profiles that fit the targeting credentials configured for a campaign.” Twitter further explains, “It’s possible that a user will see a Promoted Tweet that does not appear on the advertiser’s profile page. Advertisers have the option to send highly targeted and relevant Promoted Tweets to a specific audience only, without that Tweet being sent to all followers.”
Such messages are called Promoted-only Tweets, and “are only shown to users targeted in your campaigns.” Promoted-only Tweets, Twitter notes, “are effectively hidden,” although they are “still a part of Twitter, and can generally be found by searching for the tweet.”
Judging from its response, Trump’s was a Promoted-only Tweet, likely aimed at upcoming primary states. Makes perfect ad sense. More bang for the buck.
Among those who ignored this marketing explanation was Breitbart.com, which has a powerful motive to lie about Twitter: revenge. In January 2016, Twitter removed its coveted verified badge (little blue checkmark) from the account of Breitbart’s flamboyant technology editor, Milo Yiannopoulos, “due to violations of the Twitter Rules.” Seizing the moment, Breitbart headlined 24 hours after Trump’s promoted-only tweet, “Twitter Shadowbans Donald Trump Tweet.” Because Trump’s tweet was, as Twitter intended, effectively hidden, Breitbart alleged that “the current Republican frontrunner” had been censored.
Accordingly alarmed, The Donald’s supporters condemned this gross suppression of free speech. As @dissident_maddy put it, “Far-left Twitter shadowbanned this tweet to keep it out of circulation initially.” She and 3K others rushed to retweet Trump’s post that was, again as Twitter intended, still part of the platform.
Significantly, Trump himself remained the dog that did not bark. Neither he nor his campaign so much as breathed a word about Twitter shadowbanning him. Does anyone honestly think the outspoken Mr. Trump would not protest if he’d been so vilely mistreated by the media? We’d never hear the end of it!
Even so, what ultimately shone through was Twitter’s arrogance and stupidity in refusing to engage with its users. Instead of explaining, in a businesslike manner, that Trump’s Promoted-only Tweet behaved exactly as it was supposed to, Twitter said nothing, letting fanatics work themselves into a lather. It was almost as if Twitter’s billionaire CEO Jack Dorsey was toying with us and enjoying the show.