Open synthesis and the coronavirus pandemic in 2020

•Open Science principles are vital for ensuring reproducibility, trust, and legacy.•Evidence synthesis is a vital means of summarizing research for decision-making.•Open Synthesis is the application of Open Science principles to evidence synthesis.•Open approaches to planning, conducting, and reporting synthesis have many benefits.•We call on the evidence synthesis community to embrace Open Synthesis. Open Science principles are vital for ensuring reproducibility, trust, and legacy. Evidence synthesis is a vital means of summarizing research for decision-making. Open Synthesis is the application of Open Science principles to evidence synthesis. Open approaches to planning, conducting, and reporting synthesis have many benefits. We call on the evidence synthesis community to embrace Open Synthesis.