Observed Signal · Jul 3, 2026 · M&A - Completed · Source: Trending Topics · Impact: 3/5 · Sentiment: Positive
M&A Market: Polish software firm Callstack acquires Vienna-based Margelo
Polish software specialist Callstack is acquiring Viennese engineering firm Margelo, which develops performance libraries for React Native. The deal values Margelo at over €20 million. Margelo is known in the React Native community for its open-source libraries like Nitro Modules, VisionCamera, and react-native-mmkv, which have millions of downloads. Callstack, founded in 2016 in Wrocław, employs over 200 people and serves more than 100 enterprise clients. The acquisition follows a growth investment in Callstack in summer 2025 by US fund Viking Global Investors, which valued Callstack at around €120 million. Margelo founder Marc Rousavy will remain with the company to continue library development and work on the combined offering. Callstack aims to broaden its technology and open-source portfolio and grow internationally.
Acquisition of a niche but high-impact React Native library developer strengthens the enterprise mobile app development ecosystem.
Key Takeaways & Evidence Grounding
- Polish software-specialist Callstack is acquiring Viennese engineering company Margelo.
- Margelo is valued at over €20 million in the transaction.
- Margelo's open-source libraries include Nitro Modules (34M downloads), VisionCamera (40M downloads), and react-native-mmkv (67M downloads).
- Callstack employs over 200 people and serves over 100 enterprise customers.
- Callstack received a growth investment in summer 2025 from Viking Global Investors, valuing it at ~€120 million.
Connected Companies & Entities
3 Entities mappedViking Global
Global investment firm managing public, private, credit and structured-capital strategies.
“Damals stieg der US-Fonds Viking Global Investors mit einem Wachstumsinvestment ein...”
Margelo
React Native mobile engineering and product design agency.
“Der polnische Software-Spezialist Callstack übernimmt das Wiener Engineering-Unternehmen Margelo....”
Callstack
Enterprise React Native engineering and AI delivery services.
“Der polnische Software-Spezialist Callstack übernimmt das Wiener Engineering-Unternehmen Margelo....”
Ontology Mapping & Concepts
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