Multiline logs are logs that appear as multiple lines in a log file, often due to formatting choices like stack traces, and pose challenges for standard log shippers like Fluentd, Filebeat, and Logstash, which read log files line-by-line. This can result in each line being treated as an independent log entry, making the log data difficult to interpret. To address this issue, these shipping methods offer configuration options to pre-format and combine multiline logs into single log messages, ensuring better readability and usability. For instance, Logstash and Filebeat utilize patterns and settings like "negate" and "match" to determine whether a log line should be grouped with previous or next lines, while Fluentd uses regular expressions to define multiline start lines and patterns. Proper configuration is crucial to avoid missing log entries or incorrectly parsed log data, and tools like Coralogix provide additional features to check for and resolve multiline issues.