In last several days, I’ve tried almost all free online GTD(Getting Things Done) applications I can find. I’ve eliminated most of them through comparison, and am here to give a rough feature-based classification for the left.

GTD applications with full hierarchy:

• Todoist – project->subproject->item->subitem
• Toodledo – folder->task->subtask, but free version has no subtask feature
• Treedolist – tree of items
• Vitalist – project->subproject->action, but free version has a limit of 10 projects(including subprojects)

GTD applications with tag/label:

• HiTask – multiple tags for tasks
• Nozbe – multiple tags for projects
• Todoist – multiple labels for items
• Toodledo – single tag for tasks
• Treedolist – multiple lables for items

GTD applications with note:

• HiTask – description for tasks and stand-alone notes at the same level of tasks
• Nozbe – notes are independent elements at the same level of actions, so multiple notes can be added into one project; besides, a description can be specified for projects; notes and descriptions use the same syntax with plentiful text formats
• Toodledo – notes for tasks
• Treedolist – notes for items with Textile syntax
• Vitalist – notes with simple markup tags(a, em, strong) can be added to projects and actions

GTD applications with context:

• Nozbe – single context can be specified for actions; there are more than 10 pre-defined contexts, and new contexts can be created; meaningful icons can be specified for contexts
• Toodledo – single context can be specified for tasks
• Vitalist – multiple contexts can be specified for actions

GTD applications with priority:

• HiTask – 8 colors can be specified for tasks
• Nozbe – actions can be only marked with a star to be identified as Next Actions
• Todoist – 16 unnumbered colors can be specified for projects, 4 numbered colors can be specified for items
• Toodledo – 5 priorities can be specified for tasks: -1 Negative, 0 Low, 1 Medium, 2 High, 3 Top
• Treedolist – 2 priorities: Waiting, Urgent; in addition, font size can be adjusted to reflect different priories
• Vitalist – 3 priorities can be specified for actions: High, Medium, Low

GTD applications with grouping/ordering:

• HiTask – tasks can be grouped by date, project, color, and user
• Todoist – items can be ordered by priority and date
• Toodledo – tasks can be grouped by folder, context, goal, priority, tag, and repeat mode; tasks can be ordered by due date, due time, length, and timer
• Vitalist – actions can be grouped by context, date, project, and contact

GTD applications with filtering/searching:

• HiTask – tasks can be filtered by tag
• Nozbe – actions can be filtered by context, and projects can be filtered by tag
• Todoist – items can be filtered by date, priority, label
• Toodledo – tasks can be filtered by folder, context, goal, due date, priority, tag, recent action(add, complete, modify); tasks can be searched with all kinds of attributes
• Treedolist – items can be filtered by completion status, date, priority, label
• Vitalist – actions can be filtered by date, project, priority, context, contact; actions can be searched with complex options, including action, due date, complete date, priority, context, completion status, project, process status, contact, group by

GTD applications with time tracking:

• HiTask – starting and ending dates and times are logged for tasks
• Nozbe – time estimate can be specified for actions
• Toodledo – tasks can be tracked with timer
• Vitalist – complete date can be logged for projects and actions

GTD applications with process status:

• Vitalist – 6 statuses: inbox, actions, waiting, someday, ticklers, reference

GTD applications with drag & drop:

• HiTask – tasks can be dragged to do reordering and dropped to a different group to do reorganization
• Nozbe – simple drag & drop support to reorder actions, projects, and contexts
• Treedolist – items can be dragged around at will and dropped anywhere

GTD applications with keyboard shortcuts:

• Todoist
• Treedolist
• Vitalist

GTD applications without calender:

• Todoist – date and time need be specified with a flexible syntax

You should have noticed that as a personal user, I’m not mentioning any features as to collaboration. However, basically all online GTD applications support some kind of collaboration, not considering price.

You must be curious which one I am using. I’ve chosen HiTask at last for it offers the most complete and desirable feature subset of my need, and also a simple and nifty UI that I love.