What are hover tooltips

A hover tooltip explains the symbol under the pointer. Rest the mouse on a module name, instance, port, variable or number and the tooltip appears after a moment; from the keyboard, run Show Hover. Without leaving the current file, you can check:

• the declared type and direction of a variable or port;
• a module's declaration, parameters and file header comment;
• the width of a numeric literal and its value in each base;
• images, tables, formulas and diagrams written in declaration comments.

Verilog, SystemVerilog and VHDL are all supported.

Demo

Numeric literals

Hovering a numeric literal lists its width, signed and unsigned decimal values, and binary, octal, hexadecimal and floating-point interpretations. For example, 'h3536d238e7 is 40 bits wide with the decimal value 228553013479.

Values follow the literal as written: the leading zeros in 32'h0000_000A are only notation and the value is decimal 10; signed values also depend on the declared width. Literals containing X/Z are not ordinary integers.

Rich comments

Put the documentation immediately before a module or entity declaration and it is shown when you hover it. Comments support the following content:

Content	Comment syntax
Image	; paths resolve against the declaration file, including cross-file hovers
Table	Standard Markdown pipe table with a header separator
List	- item, 1. item; indent child items
Formula	$x^2$, a block between $$ lines, or a math / latex / tex fence
WaveDrom	A wavedrom fence containing JSON or JSON5
Flowchart	A flowchart / flow fence containing Mermaid flow syntax or basic flowchart.js definitions and connections
Sequence diagram	A sequence fence with A->B: message, B-->A: reply, participants and notes; Mermaid sequenceDiagram is also accepted
Mermaid	A mermaid fence: flowcharts, sequence, state, class and ER diagrams

Use // in Verilog/SystemVerilog and -- in VHDL; block comments with a * prefix are also supported. An excerpt from an adder's comment:

// **Formula**: $s = (a+b) \bmod 2^{W}$.
// ```mermaid
// flowchart LR
//   A[input_a] --> ADD[Add]
//   B[input_b] --> ADD
//   ADD --> S[sum]
// ```

Rendering rules:

• Line breaks and blank lines in comments are preserved; plain ------ separators do not turn earlier text into oversized headings. Module and entity tooltips exclude comments inside the implementation body.
• Raw HTML and command links are not enabled.
• Formulas and diagrams are rendered locally as SVG, with no browser or online service required, and follow the current light, dark or high-contrast theme; hover again after switching themes to see the new colors. Referenced images keep their original colors.
• Small local images are embedded, so they also display over Remote SSH; larger images keep their normal URI, and missing images keep their link.
• Mermaid supports only the diagram types in the table, not extensions such as Gantt or pie charts. Unsupported, malformed or oversized diagrams keep their source and show a message. WaveDrom never evaluates JavaScript expressions.
• Long tooltips are split between paragraphs so VS Code does not truncate image data.

In the tests/project/temp project of the Digital IDE repository, the comments in user/src/lang/svlog/lang_sv_leaf.sv and vhdl/lang_vhdl_stage.vhd cover every item in the table. Open lang_sv_core.sv and hover the instance type lang_sv_leaf, or open lang_vhdl_top.vhd and hover lang_vhdl_stage in u_vhdl_stage, to see the result.

When no tooltip appears

Make sure the pointer is on a valid identifier or number, then check the file's diagnostics, dependencies and language standard. Plain comments, whitespace and unresolved identifiers produce no tooltip.