"Microservices" has become a real buzz word in the software development community during the last couple of years. Most developers are familiar with the architectural concept which solves the problem of systems growing to large monoliths too complex to handle. This architecture has however mostly been used in backend development, even though many companies are struggling with large, monolithic frontend codebases. This is where micro frontends come in, an architectural as well as organisational approach to developing applications all the way from presentation to data layer. The micro frontends approach is relatively new, and even though there is some talk about it in the software community, many companies are unfamiliar with it, and there is very limited scientific work performed on the topic. The aim of this study was to investigate strengths of and challenges with micro frontends, and specifically how the modifiability of a web application is affected by developing it as a micro frontends project. The method for fulfilling the aim consisted of several parts. During one part, two frontend prototypes of a web application were implemented, one using a Single Page Application technique and one using a micro frontends technique. Another part consisted of interviewing practitioners in the software field with relevant backgrounds to gain their perspective on micro frontends. The results were also used to evaluate which prototype would be most suitable for the specific web application. During the last part of the method, measurements on the implemented prototypes were performed to be used to estimate the modifiability of the prototypes using a mathematical model of modifiability called SQMMA. Based on the results, this report provides an extensive summary of strengths of micro frontends, among other things that there are both beneficial and disadvantageous aspects of micro frontends when it comes to modifiability, risks that should be considered when adopting micro frontends, and a discussion on when to use it and not.

Microfrontend applications are composed of multiple smaller frontend applications, which are integrated at run-time. As with microservices, microfrontends can be updated in production at any time. There are no technological restrictions for releasing API-breaking updates. Therefore it is difficult to trust microfrontend applications to perform reliably in run-time and to introduce API-breaking updates without the risk of breaking consumers. This thesis presents Plutt, a tool that provides automatic guarantees for safely consuming microfrontends, by ensuring that updates in run-time are compatible. By using Plutt, consumers can be confident that a provided microfrontend will per- form the same during production as in development. Likewise, microfrontend providers can release updates without being concerned about how it will affect consumers. Moreover, a comprehensive survey about microfrontends is presented, where five industry experts are interviewed. Aspects that are not found in existing literature are discovered, which contributes to a broader knowledge base that helps future microfrontend research. / Mikrofrontend-applikationer är sammansatta av flera mindre frontend-applikationer som integreras under exekvering. Precis som med mikrotjänster, kan mikrofrontends bytas ut i produktion när som helst. Det saknas teknologiska restriktioner för att publicera API-brytande uppdateringar. Därför är det svårt att lita på att en mikrofrontend-applikation beter sig tillförlitligt under exekvering samt att introducera API-brytande uppdateringar utan att riskera att förstöra konsumenter. Det här examensarbetet presenterar Plutt, ett verktyg som erbjuder automatiska garantier för att säkert konsumera mikrofrontends genom att säkerställa att uppdateringar som introduceras i körtid är kompatibla. Genom att använda Plutt, kan konsumenter vara trygga i vetskapen att en försedd mikrofrontend presterar likadant under produktion som i utveckling. Samtidigt kan utvecklare som förser mikrofrontends släppa uppdateringar utan att bekymra sig över hur det påverkar konsumenter. Utöver Plutt, presenteras en grundlig kartläggning över mikrofrontends, där fem experter från industrin är intervjuade. Aspekter som inte hittas i existerande litteratur är upptäckta, vilket kunskapsbas och framtida forskning om mikrofrontends.