Block (Square until 2021) runs an unusually collaboration-first loop: instead of whiteboard algorithm quizzing, nearly every technical round is a live pair-programming session in a shared editor (CoderPad, or the candidate's own laptop/IDE in the pre-2020 era), where the interviewer works alongside the candidate and searching the web for syntax is explicitly allowed. A typical senior loop is a recruiter screen, one technical pairing phone screen, then a virtual onsite of two pairing rounds plus architecture, past-experience and leadership conversations and a hiring-manager chat; intern loops compress this to two back-to-back pairing sessions on campus followed by two more onsite. Non-engineering roles substitute a work sample: a project, case-study walkthrough or portfolio review, and data/analytics candidates get a live SQL pairing exercise as the first round.
These 5 writeups cover software engineering, data & science roles, US-centric (SF/NYC), virtual loops. 2 of them were posted under a pseudonym (Reddit, GeeksforGeeks or forum handles), so we could not verify the authors’ identities.
Typical rounds
3.81-8 range
Outcomes shared
1/1offer / not
Most common round
Technical
Sources span
2015 - 2023
Most frequently reported · Data structures & algorithms(4), Behavioral(2), Past projects(2), Scalability(2), System design(2)
Block (Square)’s official process
Block's own careers page describes a three-part process: a recruiter conversation about background and interest, a set of team interviews with the hiring team and cross-functional partners, and a role-specific work sample. For engineering that work sample is a pair-programming task; for non-engineering roles it is a project, case-study walkthrough or portfolio review. Interviews are run virtually over phone or Google Meet and the stated evaluation focus is how you collaborate and how you approach problems rather than recall. The company's engineering blog (https://developer.squareup.com/blog/ace-the-square-pairing-interview/, https://developer.squareup.com/blog/why-we-pair-interview/) adds that the pairing round is under an hour, lets you pick your own language and tools, encourages using Google/Stack Overflow, and is scored on problem comprehension, code quality and testing, communication, engineering fundamentals and getting to something that actually runs in the time available.
Data structures & algorithms·Graphs·System design·SQL·Past projects·Behavioral·Testing·API design·Domain knowledge
Interview experiences at Block (Square)
Outcome
Seniority
Software Engineer Intern
Internship
Outcome not shared4 rounds
1
On-campus pairing interview 1Technical
An on-campus session where the candidate was told to bring a laptop and code in their own environment rather than on a whiteboard, with roughly 45 minutes on the problem and 10-15 minutes of questions at the end. The interviewer worked alongside them and allowed looking up syntax and API details.
Covered · Data structures & algorithms, Testing
2
On-campus pairing interview 2Technical
A second back-to-back on-campus pairing session in the same format with a different engineer. The candidate was allowed to reuse helper code they had already written, and the interviewers asked for the written code to be sent in afterwards for the hiring decision.
Covered · Data structures & algorithms, Debugging
3
Onsite pairing interview 1Technical
A full-day onsite at the San Francisco office, with the first hour spent pairing on an algorithmic problem at a shared iMac station with a notepad available for sketching. Recruiters described the questions as rooted in algorithms and real production work.
Covered · Data structures & algorithms, Arrays & strings
4
Onsite pairing interview 2Technical
A second onsite pairing hour of comparable difficulty to the campus rounds, followed by an office tour and a short recruiter close rather than any behavioral panel.
A coding phone screen built around a graph problem the candidate rated as hard. He described the interviewer as actively coaching him toward the right direction, and he passed this stage.
Covered · Graphs, Data structures & algorithms
2
Onsite coding roundsTechnical
Virtual onsite coding sessions that he rated as the strongest part of the loop, with interviewers he found technically strong and willing to guide. He left the coding rounds feeling confident.
Covered · Data structures & algorithms, Testing
3
System designSystem design
A design round run by two interviewers where he struggled to get a conversation going; he felt they were working from a fixed question list and were not interested in exploring alternative directions.
A standard recruiter call covering why the candidate wanted to leave his current role and what he wanted next. He used it to confirm which internal level he was being considered for, noting that Square publishes its engineering career ladder.
Covered · Behavioral, Domain knowledge
2
Technical phone interviewTechnical
A coding phone interview that he prepared for by working through problems tagged to the company. The detailed write-up of this and later rounds sits behind the author's paid newsletter, so only the stage list is recorded here.
Covered · Data structures & algorithms
3
Virtual onsite, pairing 1Technical
The first of two pair-programming sessions in the virtual onsite.
Covered · Data structures & algorithms
4
Virtual onsite, pairing 2Technical
A second pair-programming session in the same onsite block.
Covered · Data structures & algorithms
5
Architecture and design discussionSystem design
A discussion-style architecture and design round rather than a coding exercise.
Covered · System design, Scalability
6
Leadership discussionBehavioral
A conversation round focused on leadership behaviour expected at the senior level.
Covered · Behavioral, Conflict handling
7
Past technical experienceBehavioral
A deep-dive on prior technical work and the candidate's specific contribution to it.
Covered · Past projects, Resume deep-dive
8
Hiring manager chatHiring manager
A closing conversation with the hiring manager, after which the process moved to an offer call and negotiation. The whole loop ran about three weeks.
An introductory phone conversation that the candidate said went well and moved quickly to the technical stage.
Covered · Behavioral, Past projects
2
Coding interviewTechnical
A live coding round in CoderPad with a single interviewer who talked through the candidate's reasoning with them as they worked. The candidate felt he did very well.
Covered · Data structures & algorithms
3
OnsiteFinal
A planned onsite involving some whiteboarding was the only remaining step, but the role was filled by a last-minute internal transfer before it was scheduled. The recruiter apologised and offered alternative openings, all of which were in San Francisco rather than New York.
Covered · Data structures & algorithms, Behavioral
A live, roughly one-hour pair-programming round in CoderPad against a PostgreSQL environment. The candidate was given two related tables, a customer table and a payments table modelling peer-to-peer transactions, and worked through four or five successive analytical questions on them; looking up syntax online was permitted.
What is the interview process like at Block (Square)?
Block (Square until 2021) runs an unusually collaboration-first loop: instead of whiteboard algorithm quizzing, nearly every technical round is a live pair-programming session in a shared editor (CoderPad, or the candidate's own laptop/IDE in the pre-2020 era), where the interviewer works alongside the candidate and searching the web for syntax is explicitly allowed. A typical senior loop is a recruiter screen, one technical pairing phone screen, then a virtual onsite of two pairing rounds plus architecture, past-experience and leadership conversations and a hiring-manager chat; intern loops compress this to two back-to-back pairing sessions on campus followed by two more onsite. Non-engineering roles substitute a work sample: a project, case-study walkthrough or portfolio review, and data/analytics candidates get a live SQL pairing exercise as the first round.
What topics does Block (Square) test in interviews?
Commonly reported topics include Data structures & algorithms, Graphs, System design, SQL, Past projects, Behavioral.
These guides summarize public, first-hand interview experiences shared by candidates. They describe the shape of each loop and the topics that came up, not a leaked question bank, and every experience links back to its original source. Processes change often. Treat this as directional prep, not a script.