10 October 2025
This article analyses the online response to the Islamist extremist Manchester synagogue terrorist attack – the first antisemitic murder in the UK in decades – and highlights how antisemitism has become increasingly normalised across digital platforms. It explores how the attack triggered a surge of antisemitic content on X (formerly Twitter) including conspiracy theories, justifications of the attack and glorification of violence. The piece also examines how extremist actors across ideological lines exploited the tragedy to advance both antisemitic and anti-Muslim narratives. Drawing on ISD’s data, the article underscores the urgent need for a comprehensive approach to counter antisemitism and extremism in the UK, rooted in the overlap between online harms and offline violence.
Key findings:
In the five days following the Manchester synagogue attack, antisemitic slurs on X increased by 28%.
ISD identified more than 6,000 antisemitic conspiracy theory-related posts from nearly 5,000 unique users, often claiming that the attack was a ‘false flag’. These posts collectively received more than 25,000 likes.
When prompted by a user, X’s AI assistant “Grok” provided speculative commentary supporting ‘false flag’ theories, reinforcing antisemitic tropes.
Extremist actors across the ideological spectrum used the attack to promote antisemitism, including victim blaming and glorification of violence. We also found anti-Muslim and anti-migrant narratives, such as calls for ‘remigration’.
Background: The antisemitic undercurrent since the 7 October attacks
The Islamist extremist terrorist attack targeting a Manchester synagogue – the first antisemitic-motivated murder in the UK for many decades – confirmed the existing fears of many British Jews. From the COVID-19 pandemic to the 7 October Hamas attacks, antisemitism both online and offline has become mainstreamed and normalised.
Antisemitism has become part and parcel of British Jewish life, spreading from fringe to popular social media platforms, hyper-charged by platform algorithms and left to proliferate unabated: 45% of British Jews reported experiencing antisemitism (either on or offline) “regularly” or “frequently” since 7 October. Violent attacks are not the only consequence of this environment: across Europe, Jewish communities are experiencing a chilling effect, withdrawing from public life and feeling unable to participate in social media as equal members of society for fear of harassment.
Calls for violence against Jews since 7 October have come from across the extremist spectrum. In the three months following the attacks, ISD research found that 12% (approximately 23,000 posts) of antisemitic comments on YouTube videos about the conflict incited violence. Tensions skyrocketed around the world – with a re-invigorated Islamist extremist landscape, an extreme-right which celebrated and sought to replicate the attacks globally, and parts of the far-left who sought to justify and celebrate Hamas’ actions, it seemed extremely likely that antisemitic attacks would occur. These have included the antisemitic rape of a Jewish girl in Paris, multiple arson attacks against Jewish sites in Australia and the murder of two Israeli embassy workers in Washington, D.C. The Community Security Trust (CST), who monitor antisemitism in the UK, recorded nine foiled terrorist plots – with a range of ideological motivations – against the British Jewish community since 2017. Two men are currently on trial for a further alleged Islamist extremist plan to attack the Jewish community in Manchester with assault weapons.
Antisemitic violence and the mainstreaming of antisemitism are inherently interconnected. This article provides an initial snapshot of this dynamic in the immediate aftermath of the Manchester synagogue attack on X, building on ISD’s previous research on the proliferation of antisemitism on the platform. Through analysis of posts on the platform, it identifies conspiracy theories about, apologism for and justifications of antisemitic terrorism. Our research since the Manchester attack shows how extremists have leveraged the tragedy for their own political gain.
Antisemitic slurs and conspiracies on X rose in response to the Manchester synagogue attack
The following section outlines antisemitic responses to the Manchester synagogue attack. It focuses on a rise in slurs, conspiracy theories and posts which glorified, justified and belittled the attack and its victims.
Rise in antisemitic slurs following the attack
Figure 1: The volume of antisemitic slurs on X over the period of a month.
Using a social listening tool, analysts used a list of high certainty antisemitism keywords to measure the changes in volume of posts containing antisemitic slurs over time. The dataset was continually refined to ensure broader anti-Israel or anti-antisemitic content was excluded. A random sample of the remaining posts was reviewed to ensure a high relevance to antisemitism, although outliers may still exist.
Figure 1 visualises the volume of slurs about Jews on X. It shows a steady drumbeat of Jew-hate across social media, only partially influenced by key events. For example, on the anniversary of the 9/11 attacks, a significant spike in online conversation was driven by conspiracy theories that Jewish people or Israelis orchestrated the attacks.
The Manchester attack prompted the third highest spike in antisemitic slurs in the past month, with a 28% increase comparing the 5 days before and after the attack. Comments included common far-right characterisations of Jewish people and classic antisemitic conspiracy theories. While many posts specifically discussed the Manchester attack, many others did not. This mirrors ISD’s findings in the aftermath of the 7 October attacks, which showed a broad range of classical antisemitic ideas were empowered by the attack as well as 20th-century antisemitism: these include conspiracy theories about Jewish money, power and influence, and medieval myths about Jews killing Jesus or drinking the blood of Christian children.
Conspiracy theories were quickly adapted to the attacks
To measure the volume of posts containing conspiracy theories about the attacks, analysts used the same social listening tool to input a list of keywords relevant to conspiracy theories and support for violence, combined with a list of indicators for the targeted Manchester synagogue.
In the five days following the attack, ISD identified more than 6,000 posts on X spreading conspiracy theories related to the attack from nearly 5,000 unique authors, including from verified blue-tick accounts (which are able to monetise their content). Six days after the attack, these posts received more than 25,000 likes and 1.7 million impressions (the number of times a post is seen in feeds or search results).
Figure 2: Graph X shows the volume of posts on X promoting conspiracy theories about the Manchester synagogue attack.
Peaking the day after the attack, a significant proportion of posts revolved around the claim that the attack was a “false flag operation orchestrated by Mossad to gain sympathy for Israeli military activity in Gaza”. Many such posts pointed to the attacker’s name as evidence for the false flag, labelling it “contrived” or obviously false. The X handle of one of the most active posters of this conspiracy included the phrase “ZioHunter”, a reference to the term ‘Zio’ as a slur for Jews used by both the far right and the far left.
After being prompted by a user to “list 10 reasons why this has the appearance of a false flag”, X’s integrated AI chatbot Grok shared several antisemitic conspiracy theories including the “timing on Yom Kippur to maximize anti-Semitic narrative” and “political gain for UK/Israel amid global tensions”. While the Grok response noted that the ideas are “speculative…with no such evidence”, it nonetheless replicated antisemitic ideas and may serve to further fuel antisemitic discourse.
Image 1. X’s chatbot Grok providing antisemitic conspiracy theories in response to a query from a user.
These antisemitic myths are not unique to the Manchester attack: conspiracy theories including distortions of the Holocaust, the false claim that Jews orchestrated the 2001 attacks on the World Trade Center and false flag claims about the 7 October attacks are regularly disseminated. Such narratives are underpinned by centuries-old antisemitic tropes that Jews are duplicitous, disloyal and secretly pulling the strings over global events.
Posts on social media justified, belittled and glorified the attack
Beyond expressing conspiratorial ideas, many posts engaged in ‘whataboutery’ and victim blaming when discussing the Manchester synagogue attack. Responses blamed the killings on Israel’s actions in Gaza, while others criticised media or official responses to the killings. Such posts suggested that sympathy for the Manchester victims was misplaced or unnecessary compared to alleged media or government indifference over suffering in Gaza and, to a lesser extent, the Gaza aid flotilla.
Fringe Muslim news website 5Pillars reported that “some speculate [the attack] may have a link to the synagogue’s support for Israel”, and referred to the targeted synagogue as a “pro-Israel synagogue”. Similarly, other blue tick accounts attempted to shift blame for the attack onto Israel or the victims themselves for their views: for example, posting that “what happened is a direct result of the illegal state of Israel, Zionism is to blame”.
Image 2. A post from the X account of 5Pillars describing the attacked synagogue as engaging in “pro-Israel activism”
Some explicitly condemned the Manchester attack but seemed to share little sympathy for the victims. For example, one account opined that the attack was “utterly vile” but that “actions have consequences” (in reference to the war in Gaza). In another example, a user appeared to praise the fear that the attack had instilled in the Jewish community, suggesting that they deserve to feel insecure due to their perceived political views.
While they may not have explicitly glorified the attack, such comments demonise victims and seek to ‘justify’ the killings to varying degrees. Much of the justification and whataboutery following the attacks rested on the assumption that British Jews are culpable for a foreign conflict, essentialising them solely as vehicles for Israeli influence.
Based on a manual review of a random data subset, only a small number of posts celebrated the attacks. These comments were more commonly found on platforms which are closely associated with far-right communities such as 4chan. Users laughed at images of the victims of the attack and posted antisemitic slurs jeering at Jews such as “remember the 6 million goyim” (which mocks Holocaust victims). Far-right antisemitism is ‘memeified’ such that antisemitic phrases have become established linguistic codes, often thrown into unrelated discourse as an in-group marker and form of crude humour. On X, some users also glorified the attacks claiming that the victims “totally deserve it” as “all Zionists everywhere are targets”.
The Manchester attack builds on the rising drumbeat of extremism
The following section highlights extremist responses to the Manchester attack and situates them in the broader context of extremist mobilisation since the 7 October attacks.
Islamist extremist groups have long called for attacks against Jews
Islamist extremist groups diverge on their vision for Palestine and support for Hamas. However, they share an antisemitic worldview and often advocate for and celebrate violence against Jews and Israel. Following the 7 October attacks, communication channels linked to the Islamic State (IS) launched a campaign targeting Jewish communities globally, named “kill them where you find them”.
This has persisted over the last two years. In the issue of al-Naba magazine (a propaganda outlet of the IS group) released on 18 September 2025, an editorial encouraged attacks against Christians and Jews everywhere. However, it had a particular focus on European countries, with calls to target Jews in countries including the UK as well as Belgium and France.
Such calls have preceded Islamist extremist attacks in multiple European countries in which the stated grievances of attackers were related to the Israel-Gaza conflict. In December 2023, an Islamist extremist killed one person in Paris; their stated motivation was seeing “so many Muslims…dying in Afghanistan and in Palestine”. In early 2024, hostages were taken at a US company office in Turkey in protest at the war; and a Jewish man was stabbed in Zurich by a boy claiming to be “heeding the call of the Islamic State to target Jews, Christians and their criminal allies”. Later that year, a teenage boy linked to IS group killed three in a knife attack in Germany “in revenge for Muslims in Palestine and everywhere”. It is not yet known whether the Manchester attacker – who reportedly pledged allegiance to IS in a 999 call after the attack – had accessed this propaganda.
Far-right networks diverged on their responses
ISD has long evidenced how extremists hijack crises to recruit and radicalise followers, including the Southport attack or the COVID-19 pandemic. The Manchester attack is no different. Attitudes towards Jews and Israel have proven a significant fissure across the far-right landscape. Radical-right networks which organise around anti-Muslim and anti-migrant hate often claim to support Jewish communities; by contrast, extreme-right ecosystems retain an antisemitic core, commonly manifesting as support for Palestine.
Users in channels associated with support for English Defence League (EDL) founder Tommy Robinson explicitly framed violence towards the Muslim community as a legitimate response, arguing that “fighting is the only way forward” and urging confrontation rather than political engagement. Robinson himself strongly condemned the attack, stating in a post with 1.2 million views that “the suspected Islamic terror attack on peaceful Jewish [sic] at their place of worship in Manchester is the consequence of Keir Starmer’s regime allowing hate marches to take to our streets”. Robinson’s pro-Israel activism caught the attention of Israeli Diaspora Minister Amichai Chikli, who subsequently invited him to Israel. This decision was strongly condemned by the leadership of the British Jewish community.
Among the wider radical-right ecosystem, various posts called for “REMIGRATION NOW” and used slur words about Muslims or migrants receiving thousands of likes – further evidencing the interconnected relationship between extremist antisemitism and anti-Muslim hate.
Extreme-right Telegram channels were quick to claim that Jews receive special treatment in the UK, including through the speed with which police responded or the outpouring of condemnation for the attack. Such ideas are central to extreme-right victimhood narratives, perceptions of the cultural and racial erosion of white Britain, and conspiracies of Jewish power and influence. For example, Laura Towler, a senior figure in white nationalist group Patriotic Alternative accused Starmer of a lack of action when British children are at risk and reserving his moral indignation for when Jews are attacked.
Others used the opportunity as evidence of the dangers of multiculturalism. Mark Collett, a leader of Patriotic Alternative, described the attack as “perfect example of a foreign dispute playing out on British soil”, arguing that the situation could easily be resolved by Muslims moving to Muslim-majority countries, and Jewish people moving to Israel. Collett also expressed concern about the attack being used to justify restrictions on freedom of expression, concluding that “everything we are seeing playing out right now is the culmination of mass immigration, multiculturalism and anti-white policy making.”
The similarities between the Manchester attack and the 2019 Yom Kippur extreme-right attack on a synagogue in Halle, Germany are emblematic of the multi-faceted threat which Jewish communities globally continue to face. The instrumentalisation of antisemitism across the extremist spectrum endangers cohesion and serves to cement structures of inequality.
Conclusions
The Islamist extremist murder of two Jewish people in Manchester on the festival of Yom Kippur exists within the wider context of the normalisation of antisemitism, the ramping up of inter-communal tensions, and the long tail of harms associated with online antisemitism. Initial attempts to explain away, dismiss or politicise the attack are emblematic of an antisemitic thought process which has sustained itself for centuries. These findings – and the attack itself – come as no surprise given deepening polarisation in the UK.
The government is now grappling with not just preventing violence but pushing back against the mainstreaming of antisemitism. This data across mainstream and fringe platforms evidences the need for a multi-tiered approach not just for mitigation but also for prevention, which addresses antisemitism’s online manifestations. With social media a clear vector for the proliferation and mainstreaming of antisemitic conspiracy theories, effective enforcement of the UK’s Online Safety Act (OSA) is central to rolling back this tide. Across Europe, antisemitic content continues to spread unabated, and Jewish communities have strong concerns about the ability of regulators to create necessary changes to stop it. Significant gaps remain in the integration of understanding of the interconnected web of legal and illegal content, insufficient transparency mechanisms, and the role of platform design functions including recommender algorithms in facilitating the spread of antisemitic content.
There is also a significant gap in the UK’s ability to prevent the interconnected landscape of hate, extremism and terrorism. ISD’s analysis articulating the need for a comprehensive human rights-based UK extremism policy strategy has suggested a holistic framework not just to prevent acts of violence but to support cohesion, human rights and democracy. A central focus of this work includes the upstream prevention of violence and bolstering of democratic norms at a local level. As the Government plans a new set of measures to push back on the normalisation of antisemitism, the centrality of online hate and its connectivity to a range of both real-world harms and solutions must not be forgotten.