The article introduces the Synthesis Without Meta-analysis (SWiM) guideline, a reporting standard designed to enhance transparency in systematic reviews that do not use meta-analysis for synthesizing effect estimates. The SWiM guideline aims to address the lack of clear reporting practices in such reviews, which can undermine the validity of the findings. The guideline covers nine key reporting items, including the grouping of studies, standardized metrics, synthesis methods, criteria for prioritizing results, investigation of heterogeneity, certainty of evidence, data presentation methods, reporting results, and limitations of the synthesis. These items are intended to provide detailed guidance on how to transparently report the methods and findings of reviews that use alternative synthesis approaches. The development of the SWiM guideline involved a Delphi exercise, expert consensus, and pilot testing to ensure its practicality and effectiveness. The guideline is particularly relevant for reviews with diverse data sources that cannot be effectively synthesized using meta-analysis, and it complements other reporting guidelines like PRISMA.The article introduces the Synthesis Without Meta-analysis (SWiM) guideline, a reporting standard designed to enhance transparency in systematic reviews that do not use meta-analysis for synthesizing effect estimates. The SWiM guideline aims to address the lack of clear reporting practices in such reviews, which can undermine the validity of the findings. The guideline covers nine key reporting items, including the grouping of studies, standardized metrics, synthesis methods, criteria for prioritizing results, investigation of heterogeneity, certainty of evidence, data presentation methods, reporting results, and limitations of the synthesis. These items are intended to provide detailed guidance on how to transparently report the methods and findings of reviews that use alternative synthesis approaches. The development of the SWiM guideline involved a Delphi exercise, expert consensus, and pilot testing to ensure its practicality and effectiveness. The guideline is particularly relevant for reviews with diverse data sources that cannot be effectively synthesized using meta-analysis, and it complements other reporting guidelines like PRISMA.