A taxonomy of behavior change techniques used in interventions was developed and tested to standardize definitions of techniques included in behavior change interventions. The study aimed to create a theory-linked taxonomy of generally applicable behavior change techniques (BCTs) to facilitate replication of effective interventions and identify techniques contributing to effectiveness across interventions. Twenty-six BCTs were defined, and two psychologists used a five-page coding manual to independently judge the presence or absence of each technique in published intervention descriptions and manuals. Three systematic reviews yielded 195 published descriptions, and across 78 reliability tests (i.e., 26 techniques applied to 3 reviews), the average Kappa per technique was 0.79 with 93% of judgments being agreements. Interventions varied widely in the range and type of techniques employed, even when targeting the same behavior among similar participants. The average agreement for intervention manuals was 85%, and a comparison of BCTs identified in 13 manuals and 13 published articles describing the same interventions generated a technique correspondence rate of 74% with most mismatches (73%) arising from identification of a technique in the manual but not in the article. These findings demonstrate the feasibility of developing standardized definitions of BCTs included in behavioral interventions and highlight problematic variability in the reporting of intervention content. The study emphasizes the need for more comprehensive categorization systems to comprehensively relate effectiveness to intervention content across behavioral domains. Standardized descriptions of intervention content would facilitate the fidelity of intervention operationalization in replication studies and applications. The present variability in intervention descriptions may inhibit faithful adoption of effective interventions, thereby curtailing their contribution to evidence-based practice. The research provides a foundational first step towards standardization and accuracy of descriptions of behavior change intervention content, as called for by CONSORT. The taxonomy includes 26 BCTs, which reflect a variety of theoretical accounts of behavior change. The study shows that psychologists can reliably judge inclusion/exclusion of these techniques from published articles and intervention manuals. The results indicate that independent coders can use the coding manual to reliably identify the same defined techniques in published intervention descriptions. The study also highlights the need for further consideration or re-definition of certain BCTs, such as technique 6 (provide general encouragement) and technique 15 (teach to use prompts). The taxonomy presented here is not exhaustive, and other techniques with a range of application across behavioral domains could be defined. The research provides a crucial first step towards establishing a common language in terms of which intervention designers, reviewers, and practitioners can clearly specify the content of behavior change interventions across domains and so clarify content differences between them. Adoption of such a taxonomy of behavior change techniques could also facilitate theory testing through meta-analytic review of intervention effectiveness.A taxonomy of behavior change techniques used in interventions was developed and tested to standardize definitions of techniques included in behavior change interventions. The study aimed to create a theory-linked taxonomy of generally applicable behavior change techniques (BCTs) to facilitate replication of effective interventions and identify techniques contributing to effectiveness across interventions. Twenty-six BCTs were defined, and two psychologists used a five-page coding manual to independently judge the presence or absence of each technique in published intervention descriptions and manuals. Three systematic reviews yielded 195 published descriptions, and across 78 reliability tests (i.e., 26 techniques applied to 3 reviews), the average Kappa per technique was 0.79 with 93% of judgments being agreements. Interventions varied widely in the range and type of techniques employed, even when targeting the same behavior among similar participants. The average agreement for intervention manuals was 85%, and a comparison of BCTs identified in 13 manuals and 13 published articles describing the same interventions generated a technique correspondence rate of 74% with most mismatches (73%) arising from identification of a technique in the manual but not in the article. These findings demonstrate the feasibility of developing standardized definitions of BCTs included in behavioral interventions and highlight problematic variability in the reporting of intervention content. The study emphasizes the need for more comprehensive categorization systems to comprehensively relate effectiveness to intervention content across behavioral domains. Standardized descriptions of intervention content would facilitate the fidelity of intervention operationalization in replication studies and applications. The present variability in intervention descriptions may inhibit faithful adoption of effective interventions, thereby curtailing their contribution to evidence-based practice. The research provides a foundational first step towards standardization and accuracy of descriptions of behavior change intervention content, as called for by CONSORT. The taxonomy includes 26 BCTs, which reflect a variety of theoretical accounts of behavior change. The study shows that psychologists can reliably judge inclusion/exclusion of these techniques from published articles and intervention manuals. The results indicate that independent coders can use the coding manual to reliably identify the same defined techniques in published intervention descriptions. The study also highlights the need for further consideration or re-definition of certain BCTs, such as technique 6 (provide general encouragement) and technique 15 (teach to use prompts). The taxonomy presented here is not exhaustive, and other techniques with a range of application across behavioral domains could be defined. The research provides a crucial first step towards establishing a common language in terms of which intervention designers, reviewers, and practitioners can clearly specify the content of behavior change interventions across domains and so clarify content differences between them. Adoption of such a taxonomy of behavior change techniques could also facilitate theory testing through meta-analytic review of intervention effectiveness.