Unexpected `variable` in weight array for font {}. You only

Error message

Unexpected `variable` in weight array for font {}. You only need `variable`, it includes all available weights.

What it means

Thrown by options_from_request() when the requested weights array contains the string 'variable' alongside other weights. 'variable' already encompasses all available weights of a variable font, so mixing it with explicit weights is contradictory and redundant.

Source

Thrown at crates/next-core/src/next_font/google/options.rs:117

            OneOrManyStrings::One(one) => vec![one],
            OneOrManyStrings::Many(many) => many,
        })
        .unwrap_or_default();

    let supports_variable_weight = font_data.weights.iter().any(|el| el == "variable");
    let weights = if requested_weights.is_empty() {
        if !supports_variable_weight {
            anyhow::bail!(
                "Missing weight for {}. Available weights: {}",
                font_family,
                font_data.weights.join(", ")
            )
        }

        FontWeights::Variable
    } else if requested_weights.contains("variable") {
        if requested_weights.len() > 1 {
            anyhow::bail!(
                "Unexpected `variable` in weight array for font {}. You only need `variable`, it \
                 includes all available weights.",
                font_family
            )
        }

        FontWeights::Variable
    } else {
        for requested_weight in &requested_weights {
            if !font_data.weights.contains(requested_weight) {
                anyhow::bail!(
                    "Unknown weight {} for font {}.\nAvailable weights: {}",
                    requested_weight,
                    font_family,
                    font_data.weights.join(", ")
                )
            }
        }

View on GitHub (pinned to 0ae8c72462)

Solutions

Use `weight: 'variable'` alone for a variable font to get all weights.
Or list only explicit numeric weights (omit 'variable') if you want a fixed subset.

Example fix

// before
const font = Inter({ subsets: ['latin'], weight: ['variable', '400'] })
// after
const font = Inter({ subsets: ['latin'], weight: 'variable' })

Defensive patterns

Strategy: validation

Prevention

When using weight 'variable', pass it alone (not in an array with other weights).
Prefer the string form weight: 'variable' over an array for variable fonts.
If you want specific weights, list them numerically and omit 'variable'.

When it happens

Trigger: Passing `weight: ['variable', '400']` (or any combination where requested_weights contains 'variable' and has length > 1) to a variable Google font.

Common situations: Misunderstanding that 'variable' is a catch-all; copy-pasting a weight list and appending 'variable'; typo in a generated config.

Related errors

AI-assisted analysis of vercel/next.js@0ae8c72462 (2026-08-06). Data as JSON: /api/errors/f887347214d8cb53. Report an issue: GitHub.